Preheat oven to 400 degrees F (200 degrees C). Lightly grease a baking sheet.
Melt butter in a large skillet over medium heat. Add onions and mushrooms; cook and stir until tender, about 5 minutes. Remove from heat and let cool slightly.
Combine creme fraiche and fromage blanc in a small bowl. Season with salt and pepper.
Spread pizza dough onto the prepared baking sheet. Spoon creme fraiche mixture on top. Cover evenly with onions, mushrooms, and bacon strips, leaving a 1-inch border. Scatter mozzarella cheese on top.
Bake in the preheated oven until crust is deep golden brown, about 15 minutes.
