|Flour||1 Cup (16 tbs)|
|Baking powder||1 Teaspoon|
|Butter||4 Ounce, softened|
|Firmly packed dark brown sugar||3⁄4 Cup (12 tbs)|
|Egg||1 (At Room Temperature)|
|Vanilla extract||1 Teaspoon|
|Semi-sweet chocolate chips||6 Ounce|
1. Preheat oven to 350°F. Grease a 9-inch square pan. In a small bowl, stir together flour, baking powder, and salt.
2. In a large bowl, beat butter with an electric mixer on medium speed until creamy. Add brown sugar and beat until fluffy. Beat in egg and vanilla until smooth.
3. Add flour mixture and beat on low speed until dough is smooth, scraping down side of bowl frequently with a rubber spatula. Turn into prepared pan, leveling surface. Sprinkle chocolate chips over batter.
4. Place in oven and bake for 3 minutes, or until chocolate begins to melt. Remove from oven and swirl a knife through dough to marbleize it. Return to oven and bake 15 to 17 minutes longer, until a toothpick inserted in center comes out with a few crumbs clinging to it. Remove pan to a rack. Let cool completely in pan before cutting into 16 squares.