Prepare the milk chocolate mousse.
Fill half of two 7in (18cm) silicon molds (Silikomart Universo 1200, 7.08in x 1.96in).
Spread the mousse to the sides of the silicon mold using an offset spatula.
Remove the inserts from the freezer and place them inside the silicon mold and press gently.
Add the additional mousse to completely fill the mold (if needed).
Remove the excess with an offset spatula.
Place in the freezer to set.
Prepare the mirror glaze, remove the frozen cakes from the freezer, and glaze immediately.
Place the cakes on a cake board.Prepare tempered white chocolate decorations with: (i) Two 1.5cm chocolate belts; (ii) Two chocolate discs (one of 9cm diameter and the other of 7.5cm diameter) and (iii) Two Christmas trees using tuile molds (Frida Molds, SH0101832).
Assemble and glue onto the 7.5cm chocolate disc.
Place the chocolate belts in the cakes.
Add the 9cm diameter chocolate ring in the center of the cake.
Place the Christmas tree on top of the chocolate disc.
Roll the white modeling chocolate to 1/8th inch.
Cut it using a small snowflake cutter.
Brush the snowflakes with gold luster dust.
Place 3 snowflakes per cake.
Let the entremets thaw completely in the fridge before serving.