Preheat oven to 375°. In a large skillet, fry bacon, drain on paper towel, reserve the drippings. Chop bacon into small pieces. Put 2-3 Tbsp. bacon drippings back into the skillet. Add the mushrooms and onions, saute for 5-7 minutes, add the spinach and bacon; cook until wilted, approximately 2 minutes. In a small bowl, combine the cream cheese with cheese ball mix. (Soften more in the microwave if needed.)
On a lightly floured surface, gently roll out the puff pastry, until it is 12 inches square. Cut pastry into a circle.
Transfer pastry onto greased pizza pan or baking sheet. Spread cheese ball mixture in the center of dough, leaving 2" border of pastry all around. Top with the spinach mixture leaving 2" border of pasty all around. Lift the pastry edges and pinch dough together to form a thick crust, overlapping the filling slightly (leave the filling exposed as much as possible). Brush edges of pastry with melted butter. Bake 45 minutes. Top with cheese and bake an additional 5 minutes or until pastry is golden brown.
Tip: Use a round pizza pan or a pie plate to get the circle shape. Lighten it up: use turkey bacon and light cream cheese instead.