Melt butter and sugar in a bowl, mix until well combined. Stir in eggs and vanilla until smooth. Gradually fold in melted chocolate.

Gently sift in flour and cocoa powder. Mix lightly until flour disappears, avoiding overmixing.

Pour brownie batter into a greased pan and bake at 350°F for 20-25 minutes or until a toothpick comes out with moist crumbs.

Let brownies cool in the pan for 15 minutes, then transfer to a wire rack to cool completely before cutting.

Shape cooled brownie squares into truffle-like balls.

Dip each truffle into pistachio cream to coat.

Roll in chopped pistachios until completely covered, and chill in the refrigerator for at least 30 minutes.

Serve chilled, optionally with vanilla ice cream or chocolate sauce.