Not claiming this is the best but it is low in fat.

2 T. butter
2 c. powdered sugar
1/4 c. cocoa
2-3 T. milk

Cream butter in small mixing bowl. Beat in half the pd. sugar & the cocoa. With mixer running dribble in a T. of milk; add remaining sugar and dribble in milk as needed for spreading consistency. Covers a 9 x 13 pan of brownies.

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This sounds good to me. A Paula Deen recipe.

4 T. butter
1 cup chopped pecans
1 cup firmly packed light brown sugar

Heat above ingred., stirring, until sugar dissolves. Drizzle over brownie batter in 9 x 13 pan and bake according to brownie directions.