Preheat oven to 400°F.
Pour oil into a large sauté pan and place over medium-high heat.
Add pancetta and sauté until crisp, about 3 minutes. Drain onto a paper towel and pour into a mixing bowl. Pour out all but 1 tablespoon of grease.
Melt butter and add leeks, shallots and garlic to the pan. Lower heat to medium low and sprinkle top with sugar. Stir and lightly season with salt.
Allow mixture to lightly caramelize for 15 to 20 minutes.
Pour mixture into the mixing bowl with pancetta and allow to cool, about 5 to 7 minutes.
Gently toss mixture together with shredded cheese and black pepper until fully combined. Season with salt.
Pour mixture into the center of the rolled out pie dough and spread evenly, leaving a 2 ½ inch perimeter around the dough.
Egg wash the perimeter of the dough and fold the edges over until sealed.
Place galette onto a baking sheet lined with parchment and bake for 20 to 25 minutes or until golden brown. Allow galette to cool for 5 minutes and serve.