Melt butter. Add shallots and heat until translucent.
Add mushrooms and continue to sauté until dry.
Add salt, pepper, Worcestershire and sherry. Continue to sauté until reduced by 1/2. Remove from heat. Let cool a little.
Add turkey, and eggs to a large bowl. Add mushroom and onion mixture. Mix to combine. Add enough bread crumbs to firm up texture.
Heat oven to 375°. Cut pizza dough. Scoop 1 ounce (or so) on cut dough squares. Fold squares over meat mixture, completely sealing. Set on prepared baking pan.
Beat 1 egg for egg wash, then brush tops of Wellingtons with egg wash
Bake balls for 30 minutes or until golden brown.
Serve with incredible mustard.