Gruyère and asparagus Dutch baby pancake

Name: Gruyère and asparagus Dutch baby pancake
Prep time: 10 min
Cook time: 50 min
Total time: 50 min
Yield: 4 portions
Ingredients: 4 eggs; 200 g milk; 130 g plain flour; 1 pinch sea salt; 40 g Gruyère cheese; 15 g unsalted butter; 20 g plain flour; 150 g milk; 1 tsp Dijon mustard; 1 pinch ground black pepper; 1 tbsp unsalted butter; 4 slices ham, shaved; 1 bunch asparagus; 3 sprigs fresh chives