Toasted Marshmallow Hot Chocolate Bars

1. Preheat the oven to 350° F. Line a 9x9 inch pan with parchment paper.
2. In the microwave, melt together the butter and 1 1/2 cups chocolate chips until melted and smooth. Stir in the sugar, hazelnut liqueur (if using), and vanilla. 
3. In a bowl, whisk the eggs for 1 minute until bubbly on top. Stir the eggs into the chocolate mix. Add the flour, cocoa powder, baking powder, and salt. Stir until just combined. Stir in the remaining 1/2 cup chocolate chips.
4. Spread half the batter into the prepared pan. Bake for 20 minutes, then remove from the oven. Switch the oven to broil. Arrange the marshmallows over the pre-baked bars. Broil for 1-3 minutes until the marshmallows are toasted to your liking. Return the oven to 350° F.
5. Spread the remaining batter over the marshmallows, covering them as best you can. It's OK if the batter doesn't cover all the marshmallows. Press the chocolate chunks into the bars. Return the bars to the oven. Bake another 20 minutes until the top is set, but the marshmallows are wiggly underneath.
6. Let the bars hang 20 minutes in the pan, then use the parchment paper to lift them out. You can let them chill or cut into them. If they're warm, they will be messier, but so DELISH! Once cool you can cut and package them for gifting!