Place the dark chocolate in a medium heat safe bowl
Place 1 cup of heavy cream in a medium saucepan, bring to a simmer (do not boil) whisk in the instant espresso powder until fully dissolved
Pour the espresso cream over the chocolate chips, add the salt and vanilla extract. Let sit for 5 minutes
After 5 minutes, whisk until the chocolate is melted and the mixture is homogenous, set aside to cool
Using beaters or the whisk attachment, beat the other 1 cup of heavy cream with ½ cup of powdered sugar until stiff peaks form, set aside
Place the mascarpone into the cooled down espresso chocolate mixture, using beaters, beat until fully combined
Fold the whipped cream into the chocolate mixture until fully combined but do not over mix, do not deflate the whipped cream
Distribute the chocolate mascarpone mousse into 6 cups, place in the refrigerator until set and completely cold
Serve cold with fresh berries and more whipped cream if desired