In the bowl of a stand mixer, whisk together 2¼ cups (281 grams) flour, granulated sugar, yeast, and salt by hand until combined. Add melted butter, warm milk, egg, egg yolk, and vanilla. Using the paddle attachment, beat at low speed until combined. Add remaining 1 cup (125 grams) flour, and beat until a shaggy dough forms, 3 to4 minutes. (Dough will be very soft but should be smooth and not overly sticky.) Cover and let rest in a warm, draft-free place (75°F/24°C) for 30 minutes.

Turn out dough onto a clean surface, and gently knead in pearl sugar. Divide dough into 6 portions (about 166 grams each).

Heat a Belgian waffle iron according to manufacturer’s instructions, and spray with cooking spray. Lightly flatten 1 portion of dough, and place on prepared iron. Cook according to manufacturer’s instructions until golden brown. Repeat with remaining dough, spraying iron with cooking spray after every other waffle. Serve warm.