First, get a large bowl and beat the eggs, milk and seasoning together in it. Melt the butter in a pan and then add the eggs. Cook over a low heat for 2-3 mins, stirring occasionally until the eggs have begun to scramble.
Next, stir in the mackerel and continue to cook until the eggs are creamy and the mackerel has warmed through.
Grab your toasted bagels on plates and divide the scrambled egg mixture between them.
Serve immediately and enjoy.