Melt half the butter in a small saucepan. Stir in flour and mustard and cook for 1 minute. Add the milk or milk alternative, stirring all the time.  Bring to the heat and simmer for a few minutes until thickened. Off the heat, stir in the cheese if using and whole grain mustard. Set aside.

Melt the remaining butter in a clean saucepan.  Add the spinach and cook over medium heat for a few minutes, stirring frequently, until just wilted. Season with salt, pepper and nutmeg. Keep warm.

Preheat oven grill to 220°C/440°F. Slice the bagels in half, and place cut side up on an oven tray. Spread each half with a spoonful of the cheese sauce. Place the tray under the grill and cook for 5-8 minutes until starts to bubble and turn golden brown.

Meanwhile, heat a frying pan, with a little vegetable oil. Crack the two eggs into the pan and cook the eggs for 3-4 minutes, until the whites are firm, and the edges are set.

Arrange the grilled bagels on two warm serving plates. Top each half with some of the wilted spinach. Arrange the slices of the Regal Cold Smoked Salmon over this, arrange one of the fried eggs on each plate. Serve immediately with any remaining cheese sauce, and a wedge of lemon or lime.