Spiced Brown Butter and Walnut Tuille Cups

Position rack in center of oven and preheat to 350°F. Line 2 large rimmed baking sheets with parchment paper or nonstick silicone baking mats. Arrange four 3/4-cup custard cups upside down on work surface.
Stir butter in heavy small saucepan over medium heat until nutty brown and milk solids are dark brown, 6 to 7 minutes. Carefully pour browned butter into small bowl and cool slightly.
Combine egg whites, sugar, five-spice powder, and salt in medium bowl; whisk until mixture is foamy, about 1 minute. Add warm browned butter, leaving dark brown milk solids behind in bowl; whisk until blended. Whisk in vanilla. Add flour and whisk until blended and smooth.
Drop batter by scant tablespoonfuls onto prepared baking sheets, spacing 4 inches apart (about 4 per sheet). Using small offset spatula, spread each to 5-inch round (batter will be spread very thin). Sprinkle generous 1/4 teaspoon finely chopped walnuts over each.
Bake tuiles, 1 sheet at a time, until evenly golden all over, about 11 minutes. Working quickly and using wide metal spatula, carefully lift each tuile from sheet and immediately drape over custard cup and press to mold to cup, making cookie bowls. Cool until tuiles are set. Carefully remove tuiles from cups and place on rack to cool completely. Repeat procedure with batter and walnuts on cool baking sheets, making total of 12 cookie bowls (to allow for any breakage). For additional cookies, if desired, drop remaining batter onto baking sheets by teaspoonfuls, spacing 2 inches apart, and bake until evenly golden. Transfer to rack and cool. DO AHEAD: Cookie bowls and cookies can be made 2 days ahead. Store airtight at room temperature.
*A spice blend that usually contains ground fennel seeds, Szechuan peppercorns, cinnamon, star anise, and cloves; available in the spice section of most supermarkets.