Heat milk in small saucepan until lukewarm, 110 to 116°F on an instant-read thermometer. Transfer the milk to the bowl of a stand mixer and add brown sugar and yeast and stir to combine. Let sit for 5 minutes or until yeast begins to form.
Add the eggs, melted butter and vanilla extract and mix with dough hook until combined.
Add 2 ⅔ cups flour and salt and mix on low speed until dough is smooth. Add remaining cup of flour and mix on low for 5 minutes, or until glossy and dough is pulling away from side of bowl.
Cover bowl with plastic wrap and place in warm place for 30 minutes.
Use your hands or a spoon to fold in the pearl sugar. Divide the dough into 10-12 balls.
Heat your waffle iron according to the manufacturer’s instructions. Working with 1 ball of dough at a time, arrange on the waffle iron and cook until golden brown all over, 2 to 5 minutes depending on your iron. Repeat with remaining dough.
If you use instant yeast, you don't have to wait for it to sit in the milk for 5 minutes.
If the dough isn't pulling away from the bowl after adding the flour, add 1 tablespoon of flour at a time until it does.
Keep the waffles in a 200°F oven while making the others to keep warm.
Clean your waffle iron while it is still warm with a damp cloth or paper towel.