Preheat the oven at 200 degrees Celsius.
Melt the butter in a casserole. Add the flour and mix together.
Add the milk and stir until the milk is boiling. Add the fish bouillon, dill, citron pepper, basil and thyme. Add some of the grated cheese and mix all well.
Place a layer of the lasagna plates on the bottom of an oven form. Cover the plates with 1/3 of the sauce, and place half of the salmon and shrimps evenly on the sauce. Repeat with another layer like this.
Cover a last layer of the plates and cover with the rest of the sauce. Sprinkle the cheese on top of the lasagna.
Place in the middle of the oven for 25 minutes. Take out and serve warm.