In a large skillet, melt the butter. Add the anchovy paste and break it up with the back of a spoon into the butter. Add the onion slices, and cook slowly. This can take up to 45 minutes. The onions will be caramelized and very golden and soft. Add them to the slow cooker. Return the skillet back to the stove. Add garlic cloves and soften for a few minutes. Add it to the also cooker.
Return the skillet back to the stove, and heat the olive oil. Trim and cut the roast into 1-2 inch pieces. Brown in the skillet until nicely caramelized. Do not overcrowd the pan, brown in the batches if need be. Move browned beef into the slow cooker as you go. Then add some of the water to the pan, about a cup's worth. Scrape the bottom of the pan and heat the water up. Add it to the slow cooker and add the rest of the water. Add the bullion, salt, and Worcestershire sauce. Cover and cook on low for 8 hours. Beef will be fork tender. If you need to add more water to get enough broth add it as you go.
Spoon the soup into oven-safe soup bowls. Place bread on top of each, and sprinkle 1/4 cup of cheese on top of the bread. Place the soup bowls onto a baking sheet and place it under the broiler on high in the oven-just until the tops are melted and bubbly and just started getting golden. Serve hot.
Servings 0