2 tbsp. butter
8 oz. fresh mushrooms
1 tbsp. minced shallot or green onions
1/2 tsp. chopped fresh parsley
8 oz. coarsely grated Gruyere cheese
8 oz. julienned rare roast beef
2 tbsp. prepared horseradish
6 (6 x 6) sq. puff pastry dough
1 egg, beaten with 1 tsp. water

SAUCE:

1 1/2 c. sour cream
1/4 c. prepared horseradish
1/4 tsp. minced garlic

Melt butter in large skillet over medium high heat. Add mushrooms, shallots, and parsley. Saute 3-4 minutes. Remove from heat and let cool. Drain well. Preheat oven to 425 degrees. Lightly grease rimmed large baking sheet. Toss cheese, beef, horseradish, and mushroom mixture in large bowl to blend. Divide mixture into 6 portions.

Place 1 puff pastry square on work surface. Spoon 1 portion of filling mixture into center of pastry. Fold up corners on pastry, pinching to seal (do not compress filling). Transfer to prepared baking sheet seam side down. Repeat with remaining portions.

Brush pastry with beaten egg mixture. Bake until puffed and golden, about 25-30 minutes.

Meanwhile, prepare sauce: Combine sour cream, horseradish, and garlic; blend well. Serve with Beef Wellington. (Kraft prepared horseradish sauce is just as good.)