Preheat the oven to 425°F (218°C) and line a baking sheet with parchment paper. Prepare the glaze by mixing the egg yolk and milk together, then set aside.
Heat the water, salt, sugar, and butter in a small saucepan, stirring until the butter is melted. Remove from heat and add the flour. Return the saucepan to the heat and stir rapidly until the mixture is smooth and pulls away from the sides of the pan.
Let the dough cool for two minutes, then beat in the eggs one at a time, mixing until smooth and shiny.
Using a small ice cream scoop, scoop up the dough and transfer it to the baking sheet. Repeat until all the dough is used. Brush the tops with the egg glaze, then press the pearl sugar or cupcake pearls onto the tops and sides of each dough.
Bake the chouquettes for about 20 to 25 minutes, or until they puff up and become light golden brown. Serve warm.