In a large bowl, mix together flour, cornmeal, and salt. Use a pastry blender or food processor to cut in butter until it's evenly distributed and a coarse crumb forms. Add the olive oil and ice water little by little until the mixture comes together. Gather the dough with your hands, form a ball, flatten into a disk, wrap with plastic and refrigerate for at least 1 hour.

Heat the olive oil in a large sauté pan. Cook the leeks for 5-7 minutes until soft and lightly browned. Stir in the garlic and corn and continue to cook for 2 minutes. Remove from the heat, stir in basil and season to taste with salt and pepper.

Preheat the oven to 375°F. Roll out the dough on a floured sheet of parchment paper to one 15-inch round or two smaller rounds. Spread the vegetable mixture into the middle of the dough leaving a 2-inch border along the sides. Sprinkle evenly with cheese. Deal out the tomato slices into a single layer then season with salt and pepper. Fold over the edges of the dough, pleating and pinching as you go. Brush the dough with egg mixture.

Lift the parchment onto the baking sheet and bake for 35 to 45 minutes until the crust is golden brown. When done, lift the parchment onto a cooling rack and cool for at least 10 minutes before slicing and serving with a garnish of basil. Can be enjoyed hot or at room temperature. Return to the oven to reheat any leftovers.