Preheat the oven to 325°F. Lightly grease (or line with parchment) two baking sheets., In a large bowl, beat together the butter, sugar, vanilla extract, almond extract, and salt., Beat in the almond flour, then the all-purpose flour., Scoop chestnut-sized (1") pieces of dough, and roll them into balls. A level teaspoon cookie scoop will give you just the right amount of dough. Place the balls on the prepared baking sheets, leaving 1" between them., Bake the cookies for 15 to 20 minutes, until they feel set on top: some of them may be starting to barely brown around the edges., While the cookies are baking, put the topping sugar in a shallow bowl., Remove the cookies from the oven, allow them to cool on the pan for a few minutes, and then transfer them, 5 or 6 at a time, to the bowl. Roll them in the sugar to coat, then transfer them to a rack to cool., When the cookies are cool, roll them in the sugar again; they should be thoroughly coated and snowy white., Store airtight at room temperature for several days; freeze for longer storage.