Preheat oven to 350 F and line a 9 by 9-inch baking pan with parchment paperUsing a double boiler, melt together butter and 1 cup of chocolate chips until smoothRemove from the stove and stir in sugar, rum (if using) and vanilla, until the sugar has dissolved.In a separate bowl, using an electric mixer, whisk the eggs for 1 minute. Stir the eggs into the chocolate mixtureAdd flour, cocoa powder and baking powder and mix to combine. Stir in remaining 1/2 cup chocolate chipsPour the mixture into prepared baking pan and bake for 30 minutes. Until the center is just set. Set aside to coolTRUFFLE TOPPINGUsing a double boiler, melt together chocolate chips with cream until smooth. Stir in nut butter and pour over the brownies. Using a knife, spread the truffle topping evenly over the topAllow the brownies to set for at least 2 hours at room temperature. Enjoy!