Preheat oven to 350º. Lightly butter 24 miniature muffin tin.
Melt together butter or margarine, semi-sweet chocolate and sugar in a small saucepan, over low heat, stirring constantly until mixture is smooth; remove from heat.
Beat in vanilla and egg, stirring until well mixed.
Fold in flour until blended.
Spoon slightly rounded teaspoon of batter into each miniature muffin tin.
Bake in 350º oven for 10-12 minutes or until center springs back when touched.
Cool in pans on rack for 10 minutes.
Remove brownie cups from pans and cool completely.
In a double boiler, melt milk chocolate over hot, not boiling water; stir until smooth.
Spread a little chocolate on top of each brownie cup using a small spatula.
Sprinkle nuts on top of chocolate.