Spinach Souffle Pie
["1 (9-inch) unbaked pastry shell", "1 egg yolk, slightly beaten", "2 c. soft bread crumbs (about 3 slices bread)", "1/2 c. milk", "3 Tbsp. Parmesan cheese, grated", "1/4 tsp. salt", "1/4 tsp. nutmeg", "1/4 c. onion, chopped", "3 Tbsp. butter", "2 pkg. frozen spinach souffle, thawed", "1 egg white"]
["Do not prick the pastry shell before baking.", "Partially bake the pastry shell in a 450\u00b0 oven for 5 minutes; remove from oven and cool on rack."]
["pastry shell", "egg yolk", "bread crumbs", "milk", "Parmesan cheese", "salt", "nutmeg", "onion", "butter", "frozen spinach souffle", "egg"]