Add 1 cup heavy cream to a saucepan over medium heat. Bring to a simmer. Pour white chocolate chips into a mixing bowl. Pour simmering cream over the top, and stir until melted and smooth. Set aside to cool.: Warmth releases the white chocolate's aroma, which is sweet and slightly milky, and you will hear a soft whisper as the cream starts to simmer. The surface will show small bubbles at the edge, signaling it is hot enough to melt the chocolate. Stirring creates a glossy emulsion, and you should see the chips dissolve into a satin sheen. This hot cream method matters because it melts the white chocolate gently, preventing graininess. If the mixture separates or looks oily, let it cool and whisk vigorously to re emulsify, or add a tiny splash of warm cream while whisking. Avoid boiling the cream, because scalding can change the texture and leave a cooked dairy flavor.
Add remaining 1 cup of cream to a large mixing bowl and beat until stiff peaks.: As you beat the cold heavy whipping cream , first it will look glossy and thick, then it will form soft peaks, and finally firm peaks that stand tall on the whisk. The sound changes from a watery slosh to a denser tap as air is incorporated. Stiff peaks mean the mousse will hold structure when folded in. If you overbeat, the cream can turn grainy or start to separate into butter and buttermilk, so stop as soon as firm peaks form. Chilling the bowl and beaters helps the cream come to peak more smoothly.
Fold into the cooled white chocolate mixture, along with 1/2 cup of the crushed candy. Cover with plastic wrap, and refrigerate for 3-4 hours.: The cooled white chocolate will smell richly sweet and look thick but pourable, and folding in the whipped heavy whipping cream brings lightness to the mixture. Use a gentle figure eight motion so you keep the air incorporated; you want a silky mousse with visible folds rather than flattened cream. Adding 1/2 cup of the peppermint candy gives speckles of mint and crunchy texture throughout. Chilling allows the mousse to firm up and the flavors to meld, resulting in a mousse that is cold and pillowy. If the mousse looks runny after chilling, it may not have been fully cooled before folding, so next time allow the chocolate base to reach near room temperature before combining.
Make the chocolate pudding and set aside.: When you prepare the chocolate pudding it should thicken until it coats the back of a spoon and gives off a warm cocoa scent. As it cools it will tighten further; smooth its surface to prevent a skin from forming, or press plastic wrap directly on the pudding to keep it glossy. The pudding layer provides concentrated chocolate flavor and a creamy body that contrasts the airy mousse. If the pudding is too thick for easy scooping, whisk it briefly to loosen; if it is too thin, allow more time to set in the refrigerator.
Make the brownies and allow to cool completely. Cut into small squares.: Freshly baked brownies will smell deeply of chocolate and will have a slightly crisp top if they were baked in a single layer. Cooling all the way is important so they hold their shape when layered, and cutting into small squares ensures even distribution in each trifle portion. Room temperature brownies absorb moisture from pudding as the dessert sits, which creates a lovely, tender bite. If the brownies are still warm, they can make the pudding and mousse looser, so always cool fully before assembling.
Cover the bottom of your serving cups (or a large trifle dish) with brownie pieces. Add spoonfuls of pudding on top.: Press the brownie pieces so they form an even bed, and the first smell you get will be rich chocolate warmth from the cake. Spoon the chocolate pudding gently to avoid displacing the brownies, creating a distinct layer that contrasts textures. The pudding acts like a glue, holding subsequent layers in place. A common mistake is overfilling early layers, which makes assembly top heavy; leave a little room to repeat layers cleanly.
Smooth a layer of mousse on top of the pudding. Repeat with 2 more layers.: When you spread the white chocolate mousse, the surface should look airy and glossy, and you will feel slight resistance as the spatula moves through it. Building two or three layers gives a pleasing height and ensures every spoonful contains each component. Layering also lets flavors meld and gives the dessert an elegant striped look. Avoid compressing the layers; gentle placement preserves the mousse's air and keeps the texture light rather than dense.
Cover with plastic wrap until ready to serve. Garnish with crushed peppermint candies just before serving.: Chilling after assembly allows the layers to settle together and the mousse to firm slightly, making clean scoops simple. When you uncover the trifle later the top will look set and inviting, and sprinkling the remaining peppermint candy adds a fresh scent and a bright visual contrast. Garnish at the last minute so the candy stays crunchy. If the candy is added too early it can soften from moisture, so keep the topping for service time.