In a heatproof bowl, whisk together 3/4 cup (180 g) heavy cream, egg yolks, 3 Tbs (38 g) sugar, and vanilla. Place bowl over a pan with an inch of simmering water, and heat, whisking continuously, until the custard coats the back of a spoon, about 165°F.

Add chocolate and whisk until melted. Set aside to cool to room temperature.

In the bowl of a stand mixer, whisk together egg whites, 1 1/2 Tbs (18 g) sugar, and a pinch of salt. Place bowl over a pan of simmering water and heat until sugar is dissolved and the mixture is opaque, about 160°F.

Place bowl on mixer fitted with the whisk attachment and whip on high until meringue holds stiff, but glossy peaks, about 3 minutes.

Using a spatula, fold the meringue into the chocolate mixture. Clean the mixer bowl and whisk attachment.

Place the remaining heavy cream (3/4 cup/180 g) in the bowl of a stand mixer fitted with the whisk attachment and whip until it holds stiff peaks, about 2 to 3 minutes.

Carefully fold whipped cream into chocolate mixture. Cover with plastic wrap and refrigerate until set, about 2 hours.