1. Heat oven to 350 degrees F. Grease a 13 x 9 x 2-inch baking pan.Brownie:
2. Combine butter and chocolate in large microwave-safe bowl. Microwave on HIGH in 30-second increments, stirring, until melted and smooth. Stir in sugar, flour, soda, salt, eggs and vanilla until smooth. Add nuts. Transfer to pan. Smooth until even.
3. Bake in 350 degrees F oven for 25 minutes.Frosting:
4. Meanwhile, combine milk, sugar, butter and egg yolks in 3-quart saucepan. Cook over medium-high heat, whisking, until bubbly, 13 to 15 minutes. Stir in pecans, coconut and vanilla; cook 2 more minutes.
5. Remove brownie from oven. Pour warm frosting over top of brownie, spreading to edges. Cool 20 minutes at room temperature. Chill 1-1/2 hours or until ready to serve.