Heat oven to 400°. Line 2 baking sheets with parchment paper.

Coarsely chop almonds and pine nuts together; set aside.

Combine butter and vanilla bean in a small saucepan. Heat over low heat, stirring occasionally, until butter is lightly golden, about 8 minutes. Remove from heat. Scrape seeds from vanilla pod and stir into butter; discard pod.

Transfer butter to a large bowl; add flour, confectioners sugar, egg white and salt. Using a rubber spatula, fold together batter just until well combined.

Drop mounds (generous 1/2 tablespoon per mound) of batter about 3 inches apart onto prepared baking sheet. Using the back of a spoon dipped in tepid water, spread each mound into a 2-inch round. Sprinkle rounds with nut mixture and Demerara sugar.

Bake, rotating pan halfway through, until edges of cookies are dark brown, about 4 minutes. Let cookies stand on baking sheet for 20 seconds (just long enough to allow them to firm up slightly), then transfer with offset spatula to rolling pin (stabilized on a cooling rack), draping them diagonally and wiping spatula clean before transferring next cookie. (If cookies become too crisp to drape, return to oven for a few seconds to soften.) Serve with Vanilla Whipped Cream.