To make vanilla wafer cookies, use all-purpose flour, aluminum-free baking powder, kosher salt and unsalted butter at room temperature. Also use a large egg, vanilla sugar, vanilla extract and whole milk. Preparation time is 25 minutes, and cook time is 20 minutes. The recipe yields 70 cookies.
Place one oven rack in the top third of the oven and a second rack in the bottom third. Preheat the oven to 350 degrees F.
In a small bowl, sift 7 ounces of flour, 3/4 teaspoon baking powder and 1/2 teaspoon salt. Using a standing mixer, beat 4 ounces butter and 3 1/2 ounces vanilla sugar at a medium speed for two minutes, scraping the sides of the bowl after one minute. Add one egg, and mix on a medium speed for an additional 30 seconds. Scrape the sides of the mixer bowl again, and pour in 4 teaspoons vanilla extract and 1 tablespoon whole milk. Beat for 15 seconds on a low speed, and pour the flour mixture into the bowl. Refrigerate the batter for 10 minutes.
Spoon the chilled batter into balls on two half-sheet pans lined with parchment paper. Flatten the scooped batter with your hand. Place both pans in the oven and bake for 20 minutes, switching the positions of the pans half way through baking. Set both pans on a cooling rack, and let cool prior to taking the cookies off the pan.