In a large bowl combine the flour, sugar,
and salt.

Cut the butter into the flour with a pastry cutter (or you can pulse in a food processor) until the mixture is crumbly.

Add the sour cream and stir until the batter comes together into a ball (again, you can use a food processor if you like).

Divide the dough ball into 2 equal pieces and roll them into balls. Wrap each ball tightly with plastic wrap and refrigerate for 45 minutes.

Slice the apples (about ⅛-inch thick ), drizzle them with lemon juice to keep them from browning too much. Cover the sliced apples with wet kitchen towel while you prepare the crust.

Preheat the oven to 350°F.

Remove the dough from the refrigerator (you can cook both at the same time or store one dough ball in the fridge for up to 4 days).

Unwrap the dough ball and place it on a sheet of parchment paper.

Roll the dough out into a flat circle, about 10 inches across. Sprinkle little flour on top if needed to prevent sticking.  Don’t worry about making a perfect circle—this galette is meant to have a rustic look, so uneven edges are fine. If the dough becomes sticky and hard to work with, put it back in the refrigerator for a bit.

Transfer the dough ball on the parchment paper onto a baking sheet. Sprinkle cornstarch all over the center of the dough (where you’re going to layer the apples), 1 teaspoon per 1 galette.

Arrange apple slices in the middle of the galette leaving about 1 ½ to 2 inches on the outer edges (those will be folded over the apples to form the edges.)

Dust the apples with cinnamon, about 1 teaspoon per galette.

Top with a few cold ice cubes.

Fold in the edges and generously brush with beaten egg yolk.

Sprinkle the coarse over the top of the galette.

Bake for 40 to 50 minutes, until the edges become beautifully golden brown.

Remove from the oven, let cool, and enjoy as is or top with caramel sauce and/or vanilla bean ice cream if you like!