Arrange 2 cooling racks on baking sheets and arrange the bacon on 1 of them. Bacon may also be baked on a slotted broiler pan. Bake the bacon until crisp, about 12 to 15 minutes. Remove the bacon to paper towels to drain.
Bring a large pot of water to a boil over medium heat. Salt the water and add the pasta. Undercook the pasta by 1 to 2 minutes, until just shy of al dente. Drain and set aside.
While the water comes to a boil, arrange the sliced tomatoes on the second baking rack. Sprinkle with chives, salt and pepper, to taste, and a drizzle of extra-virgin olive oil. Roast them for about 20 minutes. Switch the oven to broil when you remove tomatoes.
Process the bread in a food processor they become coarse bread crumbs. Transfer the bread crumbs to a small bowl.
Melt butter in sauce pot over medium heat. Pour 1/3 to 1/2 of the butter over the crumbs to moisten, then stir in the parsley. To the remaining butter in the sauce pot, add the garlic and stir for 1 minute, then add the hot sauce and mustard. Stir to combine, then sprinkle in the flour and cook for 1 minute more. Whisk in the lemon juice, Worcestershire sauce and ale. Cook for 30 seconds, then add the stock and bring to a bubble. When the sauce thickens, stir in 2 cups of the cheese in a figure 8 motion and season with salt and pepper, to taste.
Add the pasta with to the sauce and toss to coat. Spoon it into crocks or a casserole dish. Top with the bread crumbs and remaining cheese, then put it on the middle rack of the oven. Broil until bubbly and deeply brown on top, about 2 to 3 minutes.
Arrange a bed of cress leaves alongside portions of macaroni and cheese or individual crocks. Top the watercress with a thick slice of roasted tomato and crisscrossed bacon strips. Cover with a second slab of tomato and serve.