For the onions: Heat a skillet over medium-low heat and add the butter. Heat until the butter starts to foam, then add the onions and season with salt and pepper. Add thyme and bay leaf, and cook to caramelize the onions, about 30 minutes.
Deglaze the onions with the sherry and then add the stock. Reduce until just a few spoonfuls of stock remain, then keep warm.
For the sauce: In saucepot, warm the milk. In another pan, melt the butter over medium to medium-high heat and whisk in the flour and cook for 1 minute. Whisk in the warm milk, bring to a bubble, and then season with salt, pepper and some nutmeg. Cook to thicken the sauce until it coats the back of a spoon, then remove from the heat and stir in the mustard.
For the salad: In a small bowl, whisk together the vinegar, mustard and honey, and then drizzle in the olive oil. Season with salt and pepper. Add the endive, frisee and radicchio and toss to coat.
For the sandwiches: Preheat the oven to 375 degrees F. Arrange the bread on a baking sheet and top each with some caramelized onions, 2 slices ham, some bechamel and cheese. Bake the sandwiches until brown and bubbly, about 10 minutes. Meanwhile, in a large saucepan set over medium heat, add some butter and cook the eggs sunny-side up or over easy. Top the sandwiches with an egg and serve with some salad.