INSTRUCTIONS
1. Preheat the oven to 375 °F. Grease a 10-by-7-inch baking dish with the butter. Roll out the puff pastry on a lightly floured surface into a rectangle about 14 by 11 inches. Fit the dough into the prepared baking dish, letting the dough go up and extend over the sides.
2. In a large bowl, mix together the ricotta, three eggs, the mozzarella, ham, and grated cheese to combine. Spread filling over the dough, and fold the dough over to make a 13. or 2-inch border. Press holes in the top dough with a fork, and brush it with the remaining egg. Bake until the filling is set and the pastry is golden and crisp, about 40 minutes. Let the tart rest on a rack for at least 15 minutes, to set, before cutting into squares and serving.