When ready, preheat oven to 375º F.
Combine flour, sugar and salt together in a large bowl using a pastry blender or a fork. Add cold, cubed butter and combine. Slowly drizzle in ice water, one tablespoon at a time. You should have a coarse, crumbly mixture. Before the dough has formed a ball, remove dough, bringing it together by hand. Form the dough into a disc, wrap in plastic wrap and refrigerate for at least 2 hours. It’s very important to work with cold dough. Meanwhile, in a large bowl, toss apples in lemon juice, flour, sugars, cinnamon and nutmeg. Set aside. Once dough is cold, take dough out of plastic wrap and divide in half. Return one half, in plastic wrap, to the fridge. On a lightly floured surface, roll 1/2 of dough into a circle, 12-14 inches round, about 1/4-inch thick. Gently take the corners, lift the dough and transfer it to pie pan. Lightly press sides against the bottom and sides of pan. Trim overhanging dough so that you’re left with 1/2-inch and fold excess under the edge of the pan. Take second half of dough from fridge and repeat process of rolling it out to the same size. Pour apple mixture into pie pan and cover the top of apples with pats of butter. In a small bowl, beat egg yolk and add a splash of water. Brush the edges of pan, covered by the dough, with egg mixture. Cover the entire pie with remaining rolled out dough. Pierce holes in the top of dough to allow heat to escape (so there isn’t a steam buildup inside the pie). Seal edges by fluting the dough (stamping the dough with a fork or your fingers) around the edge of the pie pan. Brush egg mixture all over the top of crust and sprinkle with sugar. Bake for 50 minutes, or until crust is golden brown.