Mix first 4 ingredients in small bowl until smooth. Season garlic butter to taste with salt and pepper.Can be prepared 1 day ahead. Cover and refrigerate. Bring to room temperature before using Melt 2 tablespoons garlic butter in heavy large skillet over medium-high heat. Add mushrooms and sauteuntil tender and all liquid evaporates, about 3 minutes. Add spinach; saute until just wilted, about 1 minute. Transfer mixture to medium bowl. Cool 30 minutes. Stir in ground almonds and sour cream. Season stuffing with salt and pepper. Run fingers between chicken skin and meat to loosen (do not remove skin). Spread 2 teaspoons garlic butter under skin over meat of each chicken breast. Spoon 2 generous tablespoons stuffing under skin of each chicken breast. Using toothpicks, skewer skin to chicken to enclose stuffing. Arrange chicken on large baking sheet. Spread remaining garlic butter over top of each chicken breast.(Can be prepared 4 hours ahead. Cover and refrigerate) Preheat oven to 350F. Bake until chicken is cooked through, about 30 minutes. Transfer chicken to platter. Serves 6. Bon Appetit March 1995 Per serving: 1115 Calories (kcal); 117g Total Fat; (91% calories from fat); 9g Protein; 16g Carbohydrate; 299mg Cholesterol; 1042mg Sodium Food Exchanges: 0 Grain(Starch); 0 Lean Meat; 2 Vegetable; 0 Fruit; 23 Fat; 0 Other Carbohydrates Converted by MM_Buster v2.0n.