For mushroom filling:
1 lb. (1/2 kg. or less) fresh cultivated mushrooms chopped
1/2 medium scallion thinly sliced
1/2 cup dry white wine
1/4 cup butter
1/4 cup chopped parsley
1/2 tsp salt
1/4 tsp pepper
1. Tie the tenderloin in several places with string.
2. Rub with the soft butter and sprinkle with salt and pepper.
3. Place in an oiled shallow pan and roast in a preheated oven (475 deg. F.)(200C.)
about 20-25 minutes.
4. Remove from oven and cool 30 min. Remove string and pat dry.
5. In the meantime prepare the mushroom filling: Sauté the scallion with the butter for a minute, add mushrooms and continue sautéing for 3 minutes, add the wine and seasonings and cook for another five minutes until all liquid is absorbed. Mix in the chopped parsley. Cool for 10 minutes.
6. Lay one pastry round on a baking sheet lined with aluminum paper (keep the wax paper under the pastry).
7. Spread the mushroom filling over the whole tenderloin. Cover with the second
roll of pastry (remove wax paper). Cut excess pastry away, leaving an ample amount to seal the margins. You can cut designs from the extra pastry (for example leaves) to decorate the top.
8. Now press together the margins and roll them upwards. Gently press all around with a fork. Brush over the pastry a mixture of a beaten egg with 1 tbsp water.
Decorate if desired.
9. Roast in the preheated 400 deg.F oven (190deg C) for about 25 minutes. Remove from oven, let rest 5 minutes and serve sliced. Serve with the following sauce if desired:
Wellington sauce: Mix 1 cup beef bouillon with the drippings from the first roasting. Add 1/4 cup wine with one tbsp cornstarch mixed in, boil together for 5 minutes until thickened. Add 1 tbsp tomato concentrate. Remove from heat and stir in 1/4 cup sour cream.