Chocolate and chile is one of those combinations made in heaven, and the mango just takes it to another dimension. As always, make sure you use a good-quality chocolate, and if you can get from an Indian market a sweet, perfumed Alphonso mango, in season from April to May, so much the better.
Melt the butter in a small pan with the chopped chiles over low heat. Remove from the heat, leave to infuse for 30 minutes, then strain and discard the chiles.
Chop the chocolate into pieces and place in a large heatproof bowl. Add the infused butter and set the bowl over a pan of gently simmering water. Heat the chocolate for about 5 minutes, stirring frequently, until it melts, then remove and cool to room temperature.
Meanwhile, put the egg yolks, sugar, and 2 tablespoons of cold water in a large bowl. Place the bowl over a pan of gently simmering water. Using an electric mixer, beat the egg yolks and sugar for 5–10 minutes, until you are left with a pale, thick foam that holds a trail when the beaters are lifted up. Remove the bowl from the heat and gently fold into the cooled chocolate mixture using a large metal spoon. Let cool to room temperature.
Using a balloon whisk, softly whip the cream in a separate bowl. Using a figure-eight motion, fold the whipped cream quickly and gently into the cooled chocolate–egg yolk mixture.
Divide the mixture among 4–6 small glasses, cover with plastic wrap, and chill for at least 2 hours. When you are ready to serve, cut the mango on both sides of the pit, then peel and slice the flesh into thin wedges. Place a couple of mango slices delicately on top of each mousse and serve.
HOW TO WHIP CREAM
It is very easy to overwhip cream and cause it to go grainy if you are using an electric mixer. Whisking cream by hand is tiring but gives you more control and allows you to achieve the perfect, soft billowy texture you’re looking for.