the chocolate in a bain marie or double boiler
, about 10 minutes.
Heat the cream in a saucepan until it is just about to boil, 3 to 5 minutes. When it gets close, steam will begin to rise.
Add the cream to the melted chocolate and whisk at medium speed until combined. Whisk in the pistachio flour and the pistachio paste at medium speed until well combined.
Cool the mixture to room temperature and use as a filling for macarons, cakes or tarts.