Wash the broccoli and cut into small florets. Bring the water to a boil in a large saucepan, add salt, and pre-cook the broccoli and pasta for 4 minutes.
Drizzle the defrosted salmon with lemon juice and season with salt and pepper. Then cut the fillets into three equal pieces. Now layer the broccoli, pasta and salmon alternately in a baking dish. Mix the hollandaise sauce with the milk and the stock and pour over the casserole. Bake in a preheated oven at 180 degrees for about 20 minutes.