.In a small bowl, combine yeast and sugar with milk. Allow to sit for 10 minutes.
Pour flour into a large bowl and create a well in center. Pour yeast mixture into well, and add butter and eggs. Stir to combine, and then turn dough out onto a clean floured surface. Use your hands to knead mixture for about 10 minutes, or until a soft dough mixture. Put in a lightly oiled bowl and cover with a damp towel. Set aside and let rise in a warm place for 1 hour.
Preheat oven to 450ºF. Divide dough into golf ball-sized pieces. On a floured cookie sheet, use your hands to flatten each piece into a circle about ø-inch thick.
In a medium skillet, heat olive oil over medium heat. Add onion and sauté for 5 minutes. Add meat and cook for 5 minutes more, stirring often. Mix in parsley.
Spread a layer of topping about ∏ -inch thick in the middle of each piece of dough. Along the outside edge of each pizza, fold ø inch of dough toward center to create a border of crust.
Leave pizzas in a warm place to rise for another 30 minutes. Use a pastry brush to coat outer crusts with egg yolk (discard egg white). Bake for 5 to 10 minutes, or until golden brown.
When cooked, brush lightly with melted butter and stack in a covered saucepan for 5 minutes before serving. (This step is to soften the pastry. If you want a crisp crust, serve straight from the oven.)