1-First Step: Activate the yeast. Start by pouring 200 ml of lukewarm milk into a small bowl. Add 7 g active dry yeast and let it sit for about 5 minutes until foamy. This step matters because properly activated yeast gives the croustillons their light, airy texture. If the milk feels too hot, let it cool slightly before adding the yeast, since high heat can weaken it.

2-Second Step: Mix the dry ingredients. In a large mixing bowl, combine 250 g all-purpose flour, 10 g granulated sugar, and 5 g salt. Stir them together so the flavor is evenly spread through the batter. This dry base keeps the croustillons recipe simple and consistent, and it also helps the batter mix more smoothly once the wet ingredients go in.

3-Third Step: Add the wet ingredients. Make a well in the center of the flour mixture. Pour in the foamy yeast mixture, 1 egg, 1 teaspoon vanilla extract, and 1 tablespoon melted butter. Use a spoon or whisk to blend everything until smooth and lump-free. The batter should look soft and thick, like a loose dough. If you want to add diced apples or raisins, fold them in now before the rest period.

4-Fourth Step: Let the batter rest. Cover the bowl with a clean kitchen towel and let it rest in a warm place for 45 minutes, or until doubled in size. This resting time gives the yeast room to work and helps the dough balls puff up when they hit the oil. A warm, draft-free corner of your kitchen is ideal. If your home is cool, place the bowl near but not on a hot stove or in a barely warm oven that has been turned off.

5-Fifth Step: Heat the oil. Pour enough vegetable oil into a deep fryer or heavy-bottomed pot for deep frying. Heat it to 180°C, or 350°F. Use a thermometer if possible, because steady heat gives the best results. You can also test the temperature by dropping in a tiny bit of batter. It should sizzle right away and rise to the surface without browning too quickly. If it sinks or hardly bubbles, the oil is not hot enough yet.

6-Sixth Step: Fry the dough balls in batches. Using a spoon or small ice cream scoop, drop small portions of batter into the hot oil. Do this in batches so the oil temperature stays steady. Fry for 3 to 4 minutes, turning the dough balls occasionally so they brown evenly on all sides. The outside should turn deep golden, while the inside stays soft and tender. If the oil gets crowded, the croustillons can turn greasy instead of crisp, so patience pays off here.

7-Final Step: Drain, dust, and serve. Lift the fried dough balls out of the oil and place them on paper towels to drain. While they are still warm, dust them generously with powdered sugar. Serve immediately for the best texture, since Belgian croustillons are most crisp right after frying. The warmth, the sweet sugar, and the soft center come together in the most satisfying way.