Roasted Cherry Purée:

1. Preheat oven to 425ºF. Toss cherries with sugar in an 8" square baking dish. Bake in preheated oven for 15 minutes, stirring every 5 minutes, to soften cherries and release juices. Juices should be thickening.
2. Transfer cherries and juices to a blender and purée well, until as smooth as possible. (My blender has a soup/syrup/fondue button which I found works best.) Strain through a fine mesh sieve and discard solids. Place in a container, cover, and chill well before using.

Chocolate Mousse:

1. Heat a saucepan filled about halfway with water to bring to a simmer, preferably with a double boiler insert set on top. Prepare chocolate while water is heating.
2. Melt chocolate in a microwave-safe bowl for 30-second increments, stirring in between, until completely melted and smooth. Add butter and stir in until melted, and until the mixture is smooth once again. Strain through a fine mesh sieve into a large bowl and set aside to cool.
3. Place yolks in a medium bowl that fits over the pot or double boiler. Off of heat, whisk yolks until paler in color. Slowly pour in sugar while whisking and whisk until mixture is a pale yellow. Continue to whisk as you stream in the 2 1/8 ounces (1/4 cup) roasted cherry purée, whisking well to combine.
4. Place egg mixture over the saucepan/double boiler, making sure that whatever setup you use, the bowl with the eggs does not touch the simmering water. Whisk vigorously and constantly while eggs are over heat until mixture has paled and thickened, so that when you lift the whisk the mixture (called a sabayon) holds its shape for a brief moment before smoothing back into the remaining sabayon. DO NOT stop whisking the sabayon while over heat. Once done, remove from heat and continue to whisk until no longer warm. If you hold up the whisk, the sabayon should ribbon down from it. Strain through a fine mesh sieve (optional, if you think you may have any bits of cooked egg in your sabayon) and transfer to the bowl with the chocolate. Fold in until evenly combined.
5. In the chilled bowl of a stand mixer (or with a bowl and a hand-held electric mixer) beat cream just to stiff peaks - be careful not to overbeat. Fold into the chocolate mixture in three parts. After the final addition, fold just until the mousse is smooth, with no uneven streaks of color.
6. Pipe or spoon the chocolate mousse into 4 serving glasses, filling each halfway.* Cover the tops of each with a square of paper towel and a layer of plastic wrap on top. Chill in refrigerator as you prepare the cherry mousse.

Cherry Mousse

1. Prepare an ice bath by filling a large bowl about 1/3 of the way with ice and covering ice with cold water. Set aside.
2. Place 1 1/2 tablespoons cold water in a small bowl. Sprinkle over gelatin and stir in. Set aside while gelatin blooms.
3. In a small saucepan, stir together 5 7/8 ounces (2/3 cup) roasted cherry purée with sugar. Place over medium heat and stir slowly but constantly as the mixture comes to a low, sluggish boil. Stir and cook for an additional 30 seconds. Remove from heat and set aside to cool for 1 minute. Add gelatin and whisk in until smooth.
4. Strain cherry mixture through a fine mesh sieve into a large bowl. Place bowl over ice bath and stir constantly until the mixture has cooled and thickened.
5. In chilled bowl of stand mixer (or other bowl), beat cream just to stiff peaks - again, be careful not to overbeat. Fold into cherry mixture in three parts, continuing to fold just until the mousse is smooth and even in color.
6. Pipe or spoon cherry mousse over chocolate mousse in serving glasses.* Cover with paper towel and plastic wrap and chill for a few hours, until both mousse layers have set and are cool.

Whipped Cream:

1. Place cold water in a small bowl and sprinkle over gelatin. Stir together and let sit for 5 minutes to bloom gelatin. Microwave for 5-10 seconds at a time, stirring in between increments, just until gelatin has completely dissolved; do not let the mixture boil. Set aside.
2. In chilled bowl of stand mixer (or other bowl), whip cream just until thickened, but not quite at soft peaks. Reducing beating speed to low, slowly stream in sugar. Keep beating on low as you slowly strain the gelatin mixture through a fine-mesh sieve into the cream. Continue to beat just until stiff peaks form.
3. Pipe or spoon whipped cream on top of cherry mousse. Dip fresh cherries in sparkling sugar and place one cherry on each assembled glass of mousse. Serve immediately. Mousse can also be covered gently with plastic wrap and kept in the refrigerator for a few days. Add cherry garnish just before serving.