This is the brownie recipe I used ( I made 1 1/2 times the recipe for the number of hearts I needed).
A single recipe would probably make around 20 hearts
FUDGY FUDGE BROWNIES
1 1/4 c. flour
1/4 c. cocoa
1 tsp. baking powder
1/2 tsp. salt
2 c. sugar
3/4 c. butter, melted
1 tsp. vanilla extract
1 c. chopped walnuts (optional)
Stir together flour, cocoa, baking powder, salt and walnuts. Mix well. Set aside.
In large bowl, combine eggs, sugar, butter and vanilla. Beat with wooden spoon until smooth. Stir in dry ingredients; mix well. Spread batter evenly in 13 X 9 inch pan.
Bake in 350ºF oven for about 25 minutes. Do not overbake. Brownies are ready when edges are just set and center is still soft.
Cool on wire rack.