To make the crust, whisk together the flour, 2 tablespoons toasted sesame seeds and salt in a medium size bowl. Toss in the cold, cubed butter and then, using your fingers or a dough cutter, work the butter into the flour mixture. Try to work quickly and break the butter down into the flour mixture.

Whisk together the egg and buttermilk (or water). Create a well in the butter and flour mixture and pour in the cold buttermilk/egg mixture. Use a fork to bring the dough together. On a lightly floured work surface, dump out the dough mixture. It will be moist and shaggy. Gently knead the dough into round, flat disks.

Grease a 9 or 10 inch spring form pan with cooking spray, sprinkle the bottom and sides of the pan with toasted sesame seeds. Roll the dough out on a lightly flour surface to a 15-inch circle. Press the dough into the bottom of the prepared pan and up the sides. Line the dough with tin foil, pushing the foil down onto the dough and up and around the sides, then refrigerate for 30 minutes.

Preheat the oven to 350 degrees F. After 30 minutes, place the pan in the oven and cook for 10-15 minutes or until the crust is just set. Remove from the oven and remove the foil. Reduce the oven temperature to 325 degrees F.

Meanwhile, make the filling. Heat a large skillet over medium heat and add the butter. Once melted, add the onion and cook over medium-low heat for about 10 minutes or until caramelized. Stir in the spinach and sun-dried, cook until the spinach is wilted. Add the dried thyme and dill. Season with salt and pepper. Make sure all the moisture has cooked out of the spinach and then remove from the heat. Allow the mixture to cool 5-10 minutes and then stir in the havarti cheese, cheddar cheese and gruyere cheese. Spoon the spinach mixture into the bottom of the pre-baked pie crust.

Add the eggs, greek yogurt, milk and nutmeg to a blender and blend until smooth, about 30 seconds. Season with a little salt and pepper. Pour the egg mixture over the spinach.

Bake for 15 minutes and then remove from the oven and add the torn prosciutto. Continue to bake another hour. Allow the quiche to sit 20 minutes before cutting and then sprinkle with toasted sesame seeds and flakey sea salt.