1. Peel and finely chop the onion.
2. Wash the Swiss chard, separate the leaves from the stems.
3. Blanch the stems in boiling water for 5 to 10 minutes (until they become translucent), drain and set aside.
4. Blanch the leaves in the same water for 3 minutes, drain and set aside.
5. In a bowl, mix the milk, garlic, and flour.
6. Sauté the chopped onion in a sauté pan with oil for 5 minutes, add the stems, then the leaves. Stir everything for 5 minutes, then add the milk-flour mixture and stir for another 5 minutes.
7. Meanwhile, cook the bulgur according to the instructions.
8. In a gratin dish, arrange the bulgur, then the Swiss chard, sprinkle with breadcrumbs. Bake for 20 minutes at 180°C.