Make the crust by grating the frozen butter on a box grater. Transfer to a bowl and add the flour and salt. Using your fingers, crumble the butter into the flour until it is mostly pea sized. Add ice water, a tablespoon at a time, and stir until it forms a stiff dough. Divide in half, pat into circles, and wrap in plastic wrap. Store in the fridge until filling is done.

To make the filling, heat the oil in a heavy skillet over medium heat. Add the garlic and saute for about a minute. Add the kale, stir until wilted and add the lemon juice and zest. Turn off heat and stir in the ricotta, let cool, and stir in the egg. Season with salt and pepper.

Preheat oven to 400 degrees. Line a large baking sheet with parchment. Take out one piece of the dough and roll it on a clean surface, to about 1/4 inch thickness. Transfer to your baking sheet.

Spread the kale filling on the crust, leaving about 2 inches around the edge. Fold it up, and sprinkle the cheese on the filling. Brush the egg white over the crust.

Bake for 30-40 minutes, until cheese and crust are both browned. Remove from oven and slice into wedges before serving.