Chef Sarah Jenkins - Patisserie Enthusiast
👨‍🍳 Pastry Artist

Recipe by Mitchell

🎓 Certified Pastry Chef ⏰ 10+ Years Baking 🍽️ Cake Decorator

❤️ My Recipe Story

"I've always been fascinated by space, and I wanted to capture that wonder in a dessert. After many sticky countertops and failed glazes, I finally perfected this ratio. The contrast of the sweet, creamy mousse against the tart blueberry filling is just as beautiful as the galaxy swirl on top."

Sarah brings professional patisserie techniques to home kitchens. She specializes in demystifying complex desserts like mirror glazes and macarons, making them accessible for weekend bakers.

View All Mitchell's Recipes →
Glossy galaxy mirror glaze cake with blue and purple swirls, topped with rock candy crystals on a dark plate

The Science of Mirror Glaze

Mirror glaze (glaçage miroir) relies on the perfect temperature. If it's too hot, it will run off the cake completely, leaving a thin, see-through layer. If it's too cold, it will be lumpy and won't pour smoothly. Aim for exactly 90°F (32°C) before pouring.

The base of the cake must be frozen solid. This isn't just for structural integrity; the cold cake shocks the warm glaze, causing it to set almost instantly on the sides, creating that perfect, glossy shell without melting the mousse underneath.

💡 Professional Tip

When coloring your glaze, use an immersion blender to mix the color, but keep the head submerged to avoid introducing air bubbles. Tap the bowl on the counter to release any trapped air before pouring.

Frequently Asked Questions

Yes. The mousse needs to be rock hard so you can unmold it without dents, and the extreme cold is necessary for the warm glaze to set properly.

Gel coloring is best as it's concentrated and doesn't alter the texture. Powder can work but may leave speckles if not dissolved perfectly.

If it cooled too much, microwave it for 5-10 seconds and stir gently. Check the temperature again before pouring.

Absolutely. Use 3 sheets for the mousse and 4 sheets for the glaze. Bloom them in cold water and squeeze out excess water before melting.

Store in the refrigerator for up to 3 days. The glaze will lose its shine slightly over time, but it will still taste delicious.

Yes! Raspberry, strawberry, or mango purees work wonderfully. Just ensure the filling is frozen solid before assembling the mousse layer.

This usually happens if there is too much gelatin or if the glaze has been reheated too many times. Stick to the measurements carefully.

It tastes like a very creamy, light white chocolate cheesecake or mousse, with a sweet milky glaze and a bright pop of fruit.

Recipe Troubleshooting Guide

✅

Glaze Sliding Off

Problem: The glaze runs off leaving the cake bare

Solution: The glaze was likely too hot (above 95°F) or the cake wasn't frozen enough. Monitor temperature with a digital thermometer.

✅

Lumpy Finish

Problem: The surface is bumpy or uneven

Solution: The glaze was too cold and started setting mid-pour, or the mousse wasn't smoothed perfectly before freezing.

✅

Muddy Colors

Problem: The galaxy swirl looks brown or grey

Prevention: You overmixed the colors in the pouring cup. Pour the colors gently into one container and swirl only once or twice before pouring over the cake.

✅

Air Bubbles

Problem: Small holes or bubbles in the glaze

Recovery: Strain the glaze through a fine-mesh sieve before coloring. Avoid whipping air into it when stirring.

✅

Cake Melted

Problem: Mousse melted when glaze was applied

Prevention: The cake must be completely frozen (hard), and the glaze must not exceed 95°F. Never glaze a refrigerated cake, only a frozen one.

✅

Flavor Adjustments

Too Sweet: Add more lemon juice to the blueberry filling

Too Salty: Use salted butter in the graham cracker crust

Bland: Add vanilla bean paste to the white chocolate mousse

Baking ingredients for galaxy cake including blueberries, white chocolate, heavy cream, and food coloring on a marble counter

Choosing the Right Chocolate

For the mousse and the glaze, high-quality white chocolate is non-negotiable. Avoid 'white baking chips' or 'almond bark' which often contain no cocoa butter and are mostly vegetable oil. Real cocoa butter provides the structure and creamy mouthfeel needed.

Look for bars labeled 'couverture' if possible, or brands like Ghirardelli or Lindt. The fluidity of the chocolate affects how the glaze pours. Higher cocoa butter content usually means a smoother, thinner flow that covers the cake evenly.

Essential Ingredient Notes

  • Gelatin: Knox unflavored gelatin works well. Ensure you 'bloom' it (sprinkle over cold water) for 5 minutes before adding to hot liquids to avoid grainy lumps.
  • Blueberries: Fresh or frozen wild blueberries work best. Wild blueberries are smaller and have a more intense flavor and darker color than cultivated ones.
  • Condensed Milk: Use sweetened condensed milk, not evaporated milk. The sugar content and thickness are vital for the glaze's shine and texture.
Pouring blue and purple mirror glaze over a white frozen mousse cake, creating a galaxy effect

The Pouring Technique

This is the fun part! Place your frozen cake on a can or inverted bowl set on a baking sheet to catch drips. Pour the glaze confidently and quickly. Start in the center and spiral outward, letting gravity do the work. Do not use a spatula to spread it—this will ruin the mirror finish.

To create the galaxy effect, prepare your colors in separate cups, then pour them all into one large measuring jug. Do not mix them! Just give a single light swirl with a spoon, then pour. The colors will streak and marble naturally as they hit the cake.

Removing the Drips

Once the glaze stops dripping (about 5-10 mins), use a small knife or spatula to shave off the frozen drips hanging from the bottom edge before transferring to a serving plate.

Galaxy Cake Blueberry Delight

Prep 1 hr
Cook 20 min
Serves 10 servings
Level Advanced

📋 Ingredients

For the Mousse & Base

  • 200g granulated sugar
    Base for the syrup
  • 200g sweetened condensed milk
    Provides opacity and shine
  • 150ml water
    For the sugar syrup
  • 4 tsp gelatin powder
    Bloomed in 4 tbsp water
  • 300g white chocolate
    Chopped finely
  • Gel food coloring
    Navy, Purple, Teal, White
  • Edible glitter/stars
    For galaxy effect

For the Mirror Glaze

  • 200g graham cracker crumbs
    Or digestive biscuits
  • 85g melted butter
    Unsalted
  • 300g blueberries
    Fresh or frozen
  • 400g white chocolate
    For the mousse base
  • 600ml heavy cream
    Wipped to soft peaks
  • 2 tsp gelatin powder
    For stabilizing mousse
  • 1 tbsp lemon juice
    Brightens the blueberry flavor

Instructions

  1. Prepare Crust

    Mix graham cracker crumbs with melted butter. Press firmly into the bottom of an 8-inch springform pan or silicone mold. Freeze for 20 minutes to set.

  2. Make Blueberry Filling

    Simmer blueberries, sugar, and lemon juice in a saucepan until thickened (about 10 mins). Puree smooth or leave chunky. Stir in 1 tsp bloomed gelatin. Pour into a smaller 6-inch mold and freeze until solid.

  3. Prepare Mousse

    Melt white chocolate. Whip heavy cream to soft peaks. Dissolve 2 tsp gelatin and mix into warm chocolate. Fold whipped cream gently into the chocolate mixture until combined.

  4. Assemble and Freeze

    Pour half the mousse over the crust. Place the frozen blueberry disk in the center. Cover with remaining mousse. Smooth the top perfectly flat. Freeze overnight.

  5. Glaze and Serve

    Prepare glaze by boiling sugar, water, condensed milk, then adding gelatin and white chocolate. Color separate bowls. Cool to 90°F. Pour over frozen cake. Let drip, decorate, and thaw in fridge before serving.

Recipe Notes & Tips

Planning Ahead

This cake requires time. Make the blueberry insert and the mousse cake the day before you plan to serve. The glazing takes 20 minutes, but the cake needs 2 hours to thaw in the fridge after glazing.

Serving Suggestions

Slice with a hot knife (dipped in hot water and wiped dry) for clean cuts through the glaze and mousse. Serve with fresh blueberries on the side.

Variations

Swap the white chocolate mousse for a dark chocolate mousse for a 'Black Hole' version, or use crushed Oreo cookies for the crust instead of graham crackers.