Mirror Glaze for Mousse Cakes

Before you start

A mirror glaze is a pourable, gelatin-set coating that dries to a reflective, glass-like shine. This version uses a syrup of sugar, water and glucose, sweetened condensed milk for body, white chocolate for opacity and gelatin to make it set the moment it touches a frozen surface. The glucose keeps the sugar from crystallizing and is responsible for much of the gloss.

Temperature decides everything. The glaze should be poured at 32 to 35°C (90 to 95°F) over a cake frozen solid, ideally with a smooth surface. Too hot and it runs off thin and transparent; too cool and it lands thick and lumpy. Blend with an immersion blender held below the surface and strain the glaze, because every bubble you leave in shows up on the finished cake.

Ingredients

• 10 g (about 3½ tsp) unflavored powdered gelatin
• 60 g (¼ cup) cold water — for blooming
• 150 g (¾ cup) granulated sugar
• 75 g (⅓ cup) water — for the syrup
• 150 g (½ cup) glucose syrup — or light corn syrup
• 100 g (⅓ cup) sweetened condensed milk
• 150 g white chocolate — finely chopped, at least 28% cocoa butter
• to taste gel or powdered food coloring — water-based gel; a white coloring helps pastel shades

Method

1. Sprinkle the gelatin over the 60 g cold water and leave it for 10 minutes to bloom into a solid mass.
2. Put the chopped white chocolate in the tall container. Combine the sugar, 75 g water and glucose syrup in the saucepan over medium heat and stir until the sugar dissolves.
3. Bring the syrup to a boil and cook until it reads 103°C (217°F), about 3 minutes. Take it off the heat and stir in the condensed milk, then the bloomed gelatin until it melts completely.
4. Pour the hot mixture over the white chocolate and leave it for 1 minute. Add the coloring.
5. Tilt the container and insert the immersion blender at an angle so the head is fully submerged. Blend for about 1 minute without lifting the blade toward the surface. The glaze should turn smooth and uniform with no streaks.
6. Strain the glaze through the fine sieve into a clean jug. Tap the jug on the counter and skim off any surface bubbles. Press plastic wrap onto the surface and let it cool, stirring gently now and then without whisking.
7. When the glaze reaches 32 to 35°C (90 to 95°F), unmold the frozen cake onto a smaller base or upturned cup set on the rack over the sheet pan. Wipe off any frost so the glaze grips.
8. Pour the glaze in one continuous motion, starting in the center and spiraling outward past the edges so the sides are fully covered. Let it drip for 1 to 2 minutes, then sweep the top once with the offset spatula if needed and trim the drips from the base.
9. Move the cake to a serving board and refrigerate for at least 4 hours so the mousse thaws before serving. The glaze stays glossy as it thaws.

Tips for success

• Glaze only a frozen, smooth cake. Ridges and air pockets on the mousse show through, and a soft cake melts the glaze before it sets.
• Pour more glaze than you think you need. A thin first pass looks patchy, and a second pour over set glaze leaves a visible line.
• Collect the runoff from the sheet pan, strain it and save it. It remelts well for the next cake.

Substitutions

Glucose syrup

Light corn syrup works in equal weight. The shine is very close, though glucose syrup is thicker and gives slightly more body.

White chocolate

For a dark glaze, use 150 g dark chocolate (55–64%) and add 20 g cocoa powder to the syrup. The glaze is darker and less opaque but still glossy.

Powdered gelatin

Use 5 sheets of gold-strength sheet gelatin (about 10 g), soaked in cold water and squeezed dry. Leave out the 60 g blooming water and add 2 tbsp water to the syrup instead.

Variations

Marbled glaze

Divide the glaze into two or three jugs, color each differently, then pour them together into one jug without stirring and pour as usual.

Galaxy glaze

Color most of the glaze deep blue or black, swirl in small amounts of purple and white, and brush edible luster dust over the set glaze.

Troubleshooting

Bubbles or pinholes on the finished cake

Air was blended in. Keep the blender head submerged, strain the glaze twice and pop surface bubbles with a toothpick before pouring.

Glaze ran off thin and see-through

It was poured too hot. Let it cool to 32–35°C (90–95°F) and check with a thermometer rather than by feel.

Thick, lumpy coat with ridges

The glaze was too cool when poured. Warm it gently in the microwave in 10-second bursts, stir without whisking and recheck the temperature.

Glaze slid off the sides

The cake had frost or condensation on it, or it was not fully frozen. Freeze overnight and wipe the surface with a dry paper towel just before glazing.

Storage

Refrigerate a glazed cake and serve within 3 days. Refrigerate leftover glaze in a covered container for up to 1 week or freeze it for up to 1 month; remelt it gently to 32–35°C (90–95°F) before using.

Safety notes

Contains milk. Gelatin is made from animal collagen. The syrup is very hot; let it stop bubbling before adding the gelatin.