Favorite flavors take a new form in this easy-to-whip-up comfort-food treat.
Adjust rack to lower third of oven and preheat oven to 325 degrees F. Grease and flour an 8x8-inch baking pan.
Sift flour, baking soda, and salt onto a sheet of waxed paper, and set aside. In a medium saucepan over low heat, melt butter and chocolate and stir until smooth. Pour into a large bowl, stir in sugar, and let stand for 5 minutes. Stir in eggs, then vanilla and flour mixture. Spread batter evenly in pan and bake for 25 minutes (do not overbake).
In a bowl, toss together marshmallows and chocolate chips, then scatter mixture over hot brownie in pan. Scatter chopped nuts over marshmallows and chocolate chips, and return pan to oven for only 5 minutes. Cool thoroughly on a wire rack before cutting into squares.