In a large mixing bowl, whisk together the flour, instant yeast, sugar, and salt.

Make a well in the center and pour in the warm milk. Whisk gently until a smooth batter forms.

Add the egg and melted butter to the batter, whisking until fully incorporated.

Fold in the grated Gouda cheese and chopped scallions.

Cover the bowl with a clean kitchen towel or plastic wrap. Let the batter rest in a warm place for about 40 minutes until it becomes bubbly and slightly risen.

Heat a poffertjes pan (or a large non-stick skillet if you don't have the specialty pan) over medium heat.

Brush the indentations of the pan generously with butter or oil.

Fill a squeeze bottle or use a spoon to drop batter into the indentations, filling them about 3/4 full.

Cook for 2-3 minutes until the bottom is golden brown and the top looks nearly dry with bubbles appearing.

Use two forks or skewers to quickly flip the poffertjes over. Cook the other side for another 1-2 minutes until golden.

Remove from the pan and serve immediately while hot.