Prep the baking dish by greasing an 8x8-inch baking pan with butter or cooking spray.

Melt the marshmallow mixture by combining 4 tablespoons of butter and 6 cups of marshmallows in a medium saucepan over low heat.

Combine the dry ingredients by adding 6 cups of Rice Krispies and 1 cup of toasted pistachios to melted marshmallow mixture.

Press the mixture into the pan, aiming for a uniform thickness of about 1 to 1.5 inches.

Drizzle with chocolate by melting 1 cup of chocolate and pouring it over the set rice mixture.

Allow the mixture to set at room temperature for at least 1 hour until the chocolate has hardened.

Cut the Pistachio Rice Krispies into squares or rectangles and serve.