Preheat oven to 350 degrees F. In a large bowl, combine 2 1/4 cups flour, baking powder, and 1 teaspoon salt. Using a pastry blender or 2 knives, cut butter into flour mixture until mixture resembles coarse sand. Add 1 egg yolk, 1/2 cup chilled water, and 1/2 teaspoon vanilla and mix until just combined. (If dough is dry or crumbly and doesn’t stay together, add up to 3 tablespoons more chilled water.) Transfer dough to a lightly floured surface and knead 2 to 3 times, just until dough comes together. Return dough to bowl, cover with plastic wrap, and refrigerate until chilled, about 15 minutes. Meanwhile, make filling: In a medium bowl, combine strawberries, confectioners’ sugar, and jam, plus remaining flour, vanilla, and salt. Set aside. In a small bowl, beat remaining yolk and 1 tablespoon water for egg wash; set aside. On a lightly floured surface, roll out dough to 1/2-inch thickness. Using a 3-inch round cookie cutter, cut dough into 6 rounds.