Place the bacon in a roasting pan (about 25 cm, large enough to bake the pasta in it). Place the mold in the upper part of the oven. Remove the thick bracts and the hard part of the stalk from the cauliflower, quarter the head. Place the cauliflower quarters in a large saucepan with the cut surface facing down, add the macaroni, pour boiling water from the kettle into the saucepan and place on high heat. Salt the pasta water and drizzle in some olive oil, stir and cook with the lid halfway on according to the instructions on the packet.
Grate the cheddar in a food processor, transfer to a bowl. Take the bacon out of the oven, rinse the rosemary briefly, pat dry and remove the needles. Mix the bacon, rosemary and bread with a good dash of olive oil in the food processor until the whole thing has the consistency of coarse breadcrumbs.
Drain the pasta and cauliflower, collect the pasta water. Pour pasta and cauliflower into the pan in which the bacon was fried. Place the mold on the stove over low heat and pour in just under 400 ml of pasta water. Press in the garlic, mix in the crème fraîche and grated cheddar cheese. Gently chop the cauliflower with kitchen tongs. To taste. The pasta and cauliflower mixture should be loose and smooth, add pasta water if necessary. Spread the mixture evenly in the pan and sprinkle with breadcrumbs. Bake in the upper part of the oven for about 8-10 minutes until golden brown.
Tip:
If you want, you can sprinkle some grated Parmesan on top at the end.