How to Make It
Preheat the oven to 450°. Line a large baking sheet with parchment paper. On a lightly floured surface, roll out the dough to a 12-by-16-inch rectangle; transfer to the baking sheet. Fold the dough edge over itself to form a 1/2-inch border all around and pinch the corners together. Refrigerate until firm.
In a bowl, whisk the crème fraîche with the mustard. Spread the mixture over the dough, then sprinkle with the sauerkraut. Brush the edges with the egg wash.
Bake the galette in the bottom third of the oven for 10 minutes. Scatter the chorizo evenly over the galette and bake for 15 minutes longer, until the edges are slightly puffed. Cut the galette into squares and garnish with chives. Serve with spicy brown mustard and sauerkraut.
Learn how to make the Ultimate Savory Pie Crust dough.