Combine the warm water and yeast in a medium bowl, and let sit for 10 minutes or until doubled in volume.
Place the large bowl of a standing mixer on a kitchen scale and tare off. Weigh in 300 grams flour, sugar, eggs, and 15 grams melted butter. Mix with the dough hook attachment until a smooth dough is formed.
With mixer speed on low, slowly pour in remaining 200 grams of melted butter, mixing until it combines and a thick paste is formed (this may take 5-10 minutes). Let rest 15 minutes.
Return bowl to the kitchen scale and tare off once again. Sift remaining 200 grams flour onto dough, and sprinkle with salt.
Knead with mixer until combined. Slowly add pearl sugar and knead until combined (about 3 minutes).
Cover with plastic wrap and let rise in a warm place until doubled in volume, about 1 hour.
Preheat waffle iron on medium heat. Separate dough into balls of 100 grams each. Cook in waffle iron till pale golden brown, then remove and allow to cool completely on a wire rack. Cook waffles a second time until brown and caramelized.
Notes
Waffles may be reheated in a warm oven, or in the toaster. They freeze beautifully.