Gruyère and asparagus Dutch baby pancake

Batter

• 4 eggs
• 200 g milk
• 130 g plain flour
• 1 pinch sea salt

White sauce

• 40 g Gruyère cheese, cut into pieces
• 15 g unsalted butter
• 20 g plain flour
• 150 g milk
• 1 tsp Dijon mustard
• 1 pinch ground black pepper

Pancake

• 1 tbsp unsalted butter
• 4 slices ham, shaved
• 1 bunch asparagus, blanched, halved legthways (see Tips)
• 3 sprigs fresh chives, finely chopped, to garnish