01 -
Preheat oven to 350°F. Line 9x9 pan with parchment.
02 -
Melt butter with 1 1/2 cups chocolate chips. Stir in sugar, liqueur, and vanilla.
03 -
Whisk eggs until bubbly, stir into chocolate mixture.
04 -
Add flour, cocoa, baking powder and salt. Stir in remaining chips.
05 -
Spread half batter in pan, bake 20 minutes.
06 -
Top with marshmallows, broil 1-3 minutes until toasted.
07 -
Cover with remaining batter, add chocolate chunks, bake 20 minutes more.
08 -
Let rest 20 minutes before cutting.