HEAT oven to 350ºF. Spray a 13x9-inch pan with no-stick flour spray.
CREAM butter, sugar, vanilla and eggs in large bowl until creamy and slightly fluffy. Add milk, bananas, flour, baking powder, baking soda and salt. Beat at low speed of electric mixer until blended, scraping bowl constantly. Beat at medium speed 3 minutes, scraping bowl occasionally. Stir in nuts. Pour into prepared pan.
BAKE for 40 to 45 minutes, or until golden brown and wooden pick inserted in center comes out clean. Cool 5 minutes.
SET oven to broil. Combine butter, brown sugar and milk in small saucepan. Cook on medium heat, stirring constantly about 2 minutes, or until shortening melts. Stir in coconut and nuts. Spread over warm cake. Broil 4 inches from heat for 2 to 3 minutes, or until golden brown, watching carefully. Cool completely.