Galette Dough

1. Add the flour, sugar, and salt to a food processor. Pulse until combined.
2. Add the cold butter and pulse until the mixture resembles coarse crumbs. Stream in the cold water. The dough should come together and pull away from the sides. 
3. Transfer the dough to a clean surface and shape it into a flat, 1” disk. Wrap with plastic wrap and chill for 45 minutes.

Plum Filling & Baking the Galette

1. Preheat the oven to 400F. Line a sheet pan with a piece of parchment paper.
2. Combine the sliced plums with both sugars, the cornstarch, lemon zest, and a pinch of salt in a mixing bowl. Gently toss until well mixed. Let sit for about 20 minutes until the sugars are dissolved.
3. Meanwhile, let the chilled dough sit out at room temperature for about 10-15 minutes until soft enough to roll out. Working on a floured surface, roll out the dough to about a 12-inch circle.
4. Transfer the dough to the sheet pan. Use a slotted spoon to drain the plums and arrange them in the center of the dough, leaving a 1-inch border. Fold and pinch the edges over the plum filling. Drizzle half of the brown sugar syrup from the bowl over the plums.
5. Whisk the egg yolk and milk together to create an “egg wash”. Brush the edges with the egg wash and then sprinkle the raw sugar on top.
6. Bake the galette for 20 minutes. Drizzle the remaining syrup over the plums. Turn the pan and bake for another 10 minutes, or until the edges are golden. Let cool for about 10 minutes before slicing. Serve with ice cream.