LINE 8 x 8 x 2-inch pan with aluminum foil; GREASE foil.
COMBINE sugars in microwave-safe, 5-quart casserole.
Gradually STIR in heavy cream, beating until smooth and well blended.
MICROWAVE, uncovered, at 100% power 9 minutes, STIRRING twice; REMOVE from oven.
STIR in butter and vanilla; BEAT for 1 or 2 minutes or until mixture lightens slightly in color and thickens slightly (do not overbeat).
STIR in nuts; POUR into prepared pan; LET STAND until firmly set.
CUT into 1-inch squares; REMOVE from pan with a metal spatula.
STORE airtight at cool room temperature for up to 1 week.
Per Serving (excluding unknown items): 277 Calories; 20g Fat (62.4% calories from fat); 1g Protein; 26g Carbohydrate; 0g Dietary Fiber; 64mg Cholesterol; 99mg Sodium. Exchanges: 0 Non-Fat Milk; 4 Fat; 1 1/2 Other Carbohydrates.