Wash the fillets and dab dry. Season with salt and pepper. Wrap 1 slice of bacon around each fillet. Clean and wash spring onions and cut into large pieces. Wash and chop tarragon. Heat oil in a large coated pan.
Fry the fillets for about 3 minutes on each side. Add spring onions and fry briefly.
Remove the fillets together with the spring onions and put them into a greased casserole dish. Heat 2 tablespoons of butter in the frying fat. Sprinkle with flour and sauté briefly. Stir in 150 ml water and milk. Bring to the boil and simmer for about 3 minutes.
Stir in mustard and tarragon. Season to taste with salt, pepper and sugar.
Pour sauce over the meat. Sprinkle with cheese. Bake in the preheated oven (electric cooker: 200 °C/circulating air: 175 °C/gas: see manufacturer) for approx. 15 minutes. Baguette tastes good with it.