Bring cheeses to room temperature. Mix together in a medium-size bowl.

Mix together sour cream, horseradish mustard and onion powder. Fold into cheese mixture and blend with electric hand mixer until mixture is combined and slightly fluffy.

Line one 7½x3½x2-inch loaf pan with plastic wrap. Sprinkle half of nuts into the bottom of pan. Spread and press half of cheese mixture evenly on top of nuts. Top with remaining nuts. Spread remaining cheese mixture on top and press so that mixture is even. Cover. Chill for at least 2 hours.

To serve, invert pan onto serving plate and remove plastic. Surround with crackers, and if desired, grapes or other fruit.