In a large cast iron pan that will also work for serving, fry the bacon on medium-low heat until crisp.
Remove bacon leaving the fat. Add the shallots and soften. Then, add the garlic and thyme and sauté for another minute. Turn the heat up to medium and add the bread, stirring to coat them in the fat. Cook until the bread starts to brown. Remove and set aside.
Turn up the heat to medium-high. Add the butter and the brussel sprouts. Cook for a minute or so, until they sizzle and start to brown. Stir everything together, adding salt and pepper to tasteand transfer the pan to the oven.
Place entire pan in the oven. Cook for about 25-30 minutes, OR until the sprouts are just tender, and everything else is crisp.
Remove the thyme and sprinkle with the parmesan, and serve.