Make dough: Warm milk between 110 and 116°F, and place in the bottom of a large mixer bowl. Add sugar and yeast and stir to combine. Set aside for 5 minutes until the yeast looks foamy.
Whisk in eggs and vanilla, then stir in all but about ½ cup flour (eyeball this) using a spoon or the dough hook of a stand mixer. Once the flour is mostly combined, add the salt and continue to mix. Using the dough hook of a stand mixer, add the butter, a spoonful at a time, thoroughly kneading in each addition and scraping down the bowl as needed before adding the next until all of the butter has been mixed in. Add the remaining flour and knead with dough hook on low speed for 5 minutes, or until stretchy and glossy.
Set the dough to rise twice: You can let the dough rise two ways, first at room temperature and then in the fridge, or vice-versa:
For room temperature first, cover bowl with plastic wrap and leave at room temperature for 2 hours; dough should double. Stir with a spoon or spatula to deflate into a mound, re-cover with plastic wrap and let chill in the fridge overnight, or up to 24 hours.
For fridge first, cover bowl with plastic wrap and leave in the fridge overnight, or up to 24 hours. The dough will not look fully doubled when you take it out. The day you’d like the make the waffles, bring the dough back to room temperature for 60 minutes, stir to deflate, and let rise again for another 1 ½ to 2 hours.
To cook the waffles: For both methods, on the day you’re ready to make the waffles, knead in the pearl sugar (I did this in a few separate additions of the sugar by flattening the dough, topping with about ⅓ of the sugar, then folding it into the dough, and then repeating twice more until it becomes a homogeneous dough). Divide dough into 8 mounds. If it’s rather warm and greasy, you can return these balls of dough to the fridge until you cook them off.
Heat your waffle iron, preferably a deeper Belgian-style one, over medium to medium-high heat. No need to oil or butter if it’s nonstick and in good condition. Place the first ball of waffle dough on grid and cook according to waffle maker’s instructions (depending on your waffle iron, you may be able to cook several waffles at once–mine has a capacity for two rectangular waffles; if you have a round waffle iron, you can also fit two of these smaller waffles at a time, although the rectangular waffle iron shape is more authentic to this style waffle). Cook until deeply golden all over, which will take approximately 4 to 5 minutes, then carefully transfer with tongs or a fork to a cooling rack. Remember, they’re loaded with molten sugar; they’re very hot. Repeat with remaining balls of dough, adjusting temperature of waffle iron as needed to get the color you want. You’ll likely find that the waffles look more caramelized and glossy as you go on, as bits of melted sugar stay behind and gloss the next waffles; this is the best part but also a cause to the headache of cleaning the waffle iron–we’ll get to that later.
Keep waffles warm in a 200°F oven if you plan to eat them right away. As the waffles cool, they will harden (that’s all the melted sugar firming up), but will soften again when you rewarm them. These waffles should always be eaten warm.