Place beef in a small baking dish, and spread each filet with 1 teaspoon softened butter. Bake for 10 minutes, or until browned. Remove from pan, and allow to cool completely.
Melt 1 tablespoon butter in a skillet over medium heat. Saute onion and mushrooms in butter for 5 minutes. Add red wine and reduce for 2 minute Remove from heat, and let cool.
Roll out the puff pastry dough, cut in thirds and place beef in the center. Mix together pate and 1 tablespoon softened butter, and season with salt and pepper. Spread pate over beef. Top with onion and mushroom mixture.
Fold up, and seal all the edges, making sure the seams are not too thick. Reserve the final third of pastry for another use. (cut in half and fill with chocolate chips and raspberry jam and bake along side for an easy dessert).
Place beef in a 9x9 inch baking dish, cut a few slits in the top of the dough, and brush with melted butter.
Bake at 450 degrees F for 10 minutes, then reduce heat to 425 degrees F for 10 more minutes, or until pastry is a rich, golden brown.