Preheat your oven to 350°F (175°C). In a mixing bowl, combine molasses, brown sugar, and spices, add an egg yolk and mix in all-purpose flour until a dough forms. Roll out to 1/4-inch thickness, cut into rounds, and bake for 10-12 minutes. Cool completely.

In a small bowl, bloom the gelatin in cold water for 5 minutes. Heat espresso, brown sugar, and spices in a saucepan until steaming. Remove heat, stir in gelatin until dissolved. Melt white chocolate and combine with espresso mixture. Let cool slightly.

Whip mascarpone and heavy cream on medium speed until soft peaks form. Fold cooled espresso mixture into whipped cream gently, avoiding deflation.

Spoon the mousse into silicone dome molds, filling three-quarters full. Place cookie rounds on top, pressing gently. Tap molds to release air, cover and freeze for at least 4 hours or overnight.

Prepare mirror glaze. Remove frozen mousse domes from molds, place on a wire rack over a baking sheet, and pour glaze, allowing excess to drip off. Let sit for a few minutes.

Garnish with cocoa powder or mini gingerbread cookies if desired. Serve immediately or keep in the fridge, avoiding condensation.