Baking the flour in the oven first gives these butter cookies an irresistible nutty flavor. Serve alongside our Baked Apples.
Preheat oven to 350 degrees. Spread 1 3/4 cups flour in an even layer on a rimmed baking sheet. Bake, stirring occasionally, until flour is a light caramel color and smells slightly nutty, 30 to 40 minutes. Let cool completely.
Pass egg yolks through a fine sieve into a large bowl. Add sugar, both butters, and remaining 1 tablespoon flour; mix until well combined and a dough forms. If dough doesn't hold together, add water as needed, a little at a time. Transfer dough to a piece of parchment; roll into a log about 1 3/4 inches in diameter. Refrigerate at least 2 hours and up to overnight.
Slice log into 1/2-inch-thick rounds; transfer to parchment-lined baking sheets, spacing 1 inch apart. Brush with egg wash and sprinkle with ginger or cinnamon, if desired. Bake, rotating sheets halfway through, until cookies are golden brown around edges, 12 to 16 minutes. Transfer sheets to wire racks; let cool completely.