A savory tart is ready to be served on vintage majolica plates.
Preheat oven to 375 degrees. Cook bacon in a skillet over medium heat until crisp, about 8 minutes. Using a slotted spoon, transfer to a bowl. Add garlic and onion to skillet. Cook until onion is translucent, about 5 minutes. Add to bacon.
Return skillet to heat, and melt 1/2 tablespoon butter. Add 1 1/2 cups mushrooms and 1/4 teaspoon salt, and cook until golden on edges and softened, about 5 minutes. Transfer to a plate. Repeat with remaining 1/2 tablespoon butter and 1 1/2 cups mushrooms. Stir cream and mustard into last batch in skillet, and cook for 30 seconds. Add to bacon-onion mixture, along with first batch of mushrooms. Let cool.
Roll out pate brisee to a 12-by-18-inch rectangle (about 1/8 inch thick) on a lightly floured surface. Transfer to a parchment-lined baking sheet. Spread mushroom-bacon mixture over dough, leaving a 3-inch border. Tuck tomatoes into filling, leaving some poking out. Sprinkle with cheddar. Fold in edges to form a 6-inch-wide open-topped crust; brush crust with egg wash. Bake until golden brown and center is bubbling, about 55 minutes. Serve warm or at room temperature.