This recipe makes one 8 inch galette or two 4 inch galettes.
1 ¼ cups (160 g) all-purpose flour, plus more for dusting
1 tsp (6 g) kosher salt
5 oz unsalted butter, diced and refrigerated
¼ -½ cup ice water
Egg wash and sugar topping::
1 lbs (about 4 cups or 250 g) rhubarb, trimmed and cut into ¾ inch (1.9 cm) pieces
⅓ cup (200 g) sugar
2 tsp (10 g) molasses
½ tsp (1 g) cinnamon
Heavy pinch of salt
Combine the flour and salt in a bowl. Add the butter to the bowl and use your fingers to break the butter pieces into smaller pieces, about the size of a pea. It is okay to have a few larger pieces as long as the butter stays very cold. Slowly add the water, mixing with your hands until the dough begins to form. The dough should be very shaggy and dry, if all of the dough will not come together add a little more water.
Working quickly so the butter does not begin to melt, turn the dough out onto a lightly floured surface and shape it into a ball. Wrap the dough in plastic wrap and rest in the refrigerator for 30 minutes. Remove dough from the refrigerator and flatten into a flat disc. Wrap the dough back in the plastic wrap and place in the refrigerator for 1 hour. The dough can keep in the refrigerator for up to 3 days or it can be frozen for 3 months. If frozen, thaw the dough in the refrigerator the night before using.
To make the filling combine the rhubarb, sugar, molasses, cinnamon and salt in a medium bowl and toss together to coat the rhubarb. Let the mixture rest for at least 1 hour.
Preheat the oven to 450 degrees.
When ready to assemble the galette heavily flour a work surface and rolling pin. Roll the dough out into a ten inch circle (if making two smaller galettes divide the dough in half and roll into two 5 inch rounds). Transfer the dough to a piece of parchment paper and place on a large baking sheet. Remove the rhubarb from the macerating liquid (save the liquid) and line the inside of the dough round with the rhubarb pieces (create your own design pattern or simply spread the rhubarb), leaving a 1 inch border around the edges. Fold the dough border over the edge of the rhubarb, making a fold every couple of inches.
In a small bowl make an egg wash by thoroughly whisking an egg with the leftover macerating liquid. Using a pastry brush spread the egg wash over the top of your crust. Sprinkle the egg washed dough with a very liberal amount of raw sugar.
Bake the galette for about 30 minutes or until the crust is a nice golden brown, the rhubarb is soft and the filling begins to bubble. Let the galette cool for 30 minutes before serving. The galette is best served warm, topped with ice cream or whipped cream.