Put the salmon in the bottom of a casserole dish. Use 1
tbsp of the margarine and 1/4 cup of the milk to beat the potatoes
until smooth.
Make a white sauce with the remaining ingredients as follows:
Melt the margarine in a sauce pan, and add the flour, stirring in slowly to
avoid lumps. Add the milk and stir constantly until thick.
Pour the white sauce over the salmon, and then top with the
potatoes.
Bake at 400 degrees until the sauce bubbles.