Food Network teaches how to crush, slice and mince garlic. Peel off some of the papery skin from the garlic and then smash the head of garlic with the heel of your hand to loosen the cloves; if you only need a few cloves, leave the head intact and pull some off. Separate the cloves. To peel a clove, cut away the root end with your knife. Lay the flat side of the knife over the clove while holding the knife handle, then with the heel of your free hand carefully whack the knife against the garlic to separate the skin from the clove. To crush the peeled garlic, lay the flat side of the knife over the clove and smash it again. To slice peeled garlic, lay the clove flat on the cutting board and hold it with the fingertips of one hand, keeping them curled under. Using a rocking motion with the knife, make thin slices by moving the knife slowly across the clove. To mince peeled garlic, lay the flat side of a knife over the clove and smash it. Roughly chop the clove then move your free hand flat across the tip of the knife and use a rocking motion to chop the garlic until it’s finely minced.
For the crust: Place an oven rack in the center of the oven. Preheat the oven to 450 degrees F. Dust a heavy baking sheet with cornmeal. Set aside.
On a lightly floured work surface, roll out the dough into a 1/4-inch thick rectangle about 16 inches long and 8 inches wide. Transfer the dough to the prepared baking sheet.
For the topping: In a large skillet, heat the oil over medium-high heat. Add the leeks and season with salt and pepper. Cook, stirring frequently until tender, about 5 minutes. Add the garlic and cook for 30 seconds until aromatic. In batches, add the spinach and cook until wilted, about 5 minutes. Remove the pan from the heat and add the feta cheese and mint. Season with salt and pepper, to taste.
Using the tines of a fork, prick the surface of the dough all over. Spread the spinach mixture on top and dot with butter.
Bake until the dough is golden and crunchy, 15 to 18 minutes. Cut into squares and serve.