I made these, too. Haven't eaten one yet, but they sure are cute! UPDATE: these were a little underdone. I think I'd bake them for 30 minutes.
Courtesy of Baked Perfection: http://www.bakedperfection.com/2009/02/brown-sugar-blondies-for-valentines-day.html
1 cup all-purpose flour
1/2 teaspoon baking powder
1/8 teaspoon baking soda
1/2 teaspoon salt
1/3 cup butter
1 cup packed brown sugar
1 tablespoon vanilla extract
1 cup to 1 1/3 cup M&M's
Preheat oven to 350 degrees F (180 degrees C).
Mix together flour, baking powder, baking soda, and salt and set aside. Melt 1/3 cup butter. Add 1 cup firmly packed brown sugar and mix well. Cool slightly. Add egg (beaten) and vanilla and blend well. Add flour mixture, a little at a time, mixing well. Mix in 2/3 cup M&M's. Spread in 9 x 9 x 2 inch pan. Sprinkle 1/3 to 2/3 cup M&M's on top. Bake for 20 to 25 minutes. Store in airtight container at room temperature.