Preheat oven to 350 degrees F. For buttered pecans, spread pecans in a shallow baking pan; dot with the 3 Tbsp. butter. Bake 6 to 8 minutes or until toasted, stirring occasionally. Let cool.
Meanwhile, grease and lightly flour two 8-inch round cake pans. In a medium bowl stir together flour, baking powder, and salt.
In a large bowl beat the 2/3 cup butter with a mixer on medium to high 30 seconds. Gradually add sugar, 1/4 cup at a time, beating on medium until well combined. Scrape sides of bowl; beat 2 minutes more. Add eggs, one at a time, beating well after each addition. Beat in vanilla. Add flour mixture and milk alternately, beating on low after each addition just until combined. Beat on medium to high 20 seconds more. Fold in 1 cup of the buttered pecans. Spread batter evenly into prepared pans.
Bake 30 to 35 minutes or until a toothpick comes out clean. Cool cake layers in pans on wire racks for 10 minutes. Remove layers from pans; cool on wire racks. Frost with Vanilla Frosting. Decorate with remaining buttered pecans.
In a medium bowl beat butter and vanilla with a mixer on medium until light and fluffy. Gradually beat in half of the powdered sugar. Add 4 Tbsp. of the half-and-half. Gradually beat in the remaining powdered sugar and half-and-half until spreading consistency.