1 stick (1/4 lb.) unsalted butter
1 cup chocolate graham cracker or chocolate wafer crumbs (12 cookies)
2 tablespoons packed light brown sugar
1/4 teaspoon plus a pinch of salt
2 ounces unsweetened chocolate, chopped
3/4 cup sugar
1 teaspoon vanilla extract
2 large eggs
1/2 cup all-purpose flour
2 cups mini marshmallows
1/2 cup semisweet chocolate chips
- Preheat oven to 350°F. Butter an 8-inch, square pan and line with parchment paper.
- Melt half of butter and then mix with crumbs, brown sugar and a pinch of salt. Press firmly into bottom of pan. Bake in bottom third of oven until set, 10 to 12 minutes.
- Combine remaining butter and unsweetened chocolate in a heatproof bowl; microwave at 20-second intervals until melted, stirring after each interval. Cool slightly. In a separate bowl, whisk sugar, vanilla and eggs. Stir in chocolate mixture. Add flour and mix until just combined. Pour over cooled crust and bake until just set, 22 minutes.
- Remove from oven. Set broiler on high and place oven rack 3 inches from heat. Sprinkle marshmallows and chocolate chips over cookie and broil until marshmallows start to brown, 1 minute. Remove from oven and let cool before cutting into squares.