Preheat the oven to 350 degrees.

Combine the butter and chocolate in a bowl set over a saucepan of boiling water and melt, stirring occasionally. In a large mixing bowl, whisk the eggs, light brown sugar, vanilla and salt. Slowly whisk in the melted chocolate mixture. Fold in the flour, until just blended.

Spray a 12″ x 17″ rimmed baking sheet with nonstick cooking spray and pour in the batter. Use a spatula to smooth it evenly.

Bake for 10 minutes. Transfer the pan to a rack and cool.
Break up the brownie pieces into the bowl of an electric mixer fitted with a paddle attachment. Beat on low until they are completely broken up. Slowly add in the rum, a bit at a time, and beat until the mixture forms into a ball. You will know it’s the right texture if you can easily roll the dough and it holds its shape.

Scoop out the dough by the tablespoon and roll into a ball. Toss in sanding sugar and chill until ready to serve.

(Recipe adapted from Martha Stewart.)