Whisk together the flour, sugar, baking powder, and salt in a medium mixing bowl.

In a separate bowl, whisk the egg, milk, melted butter, and vanilla extract until emulsified.

Combine the wet and dry ingredients, stirring until just incorporated; minor lumps are acceptable.

Preheat a non-stick skillet or a multi-cavity pancake puff pan over medium heat and lightly grease with oil or butter.

Transfer the batter into a piping bag or use a small teaspoon to drop 1-tablespoon portions onto the heated surface.

Cook for approximately 90 seconds until bubbles form on the surface and the edges appear set.

Flip each popper using a skewer or small spatula and cook for an additional 60 seconds until golden brown and cooked through.

Remove from heat and serve immediately.