1 1/2 c. walnuts, chopped coarse
2/3 c. butter
1 c. packed light brown sugar
1 c. (14 oz.) sweetened condensed milk (not evaporated)
1 1/2 tsp. vanilla

Line 8x8 square pan with foil, letting foil extend over sides. Grease lightly. Spread nuts in a 9-inch microsafe pie plate; cook uncovered on high 6-7 minutes, stirring 3 times until lightly toasted.

Melt butter in a 2 1/2 or 3-quart microsafe bowl. Stir in sugar and milk until blended. Micro uncovered on high 7-9 minutes, stirring 4 times, until sugar has completely dissolved, and mixture has thickened and is a medium caramel color. Add vanilla.

Beat with electric mixer 3-4 minutes until smooth and satiny. Add walnuts and beat at low speed 1 minute to distribute evenly. Spread in prepared pan. Cool, then cover and refrigerate until firm, 2-3 hours. Lift foil gently and peel off candy. Cut into 1-inch squares. Store in tightly covered cool place.