Prep 1 bunch of broccoli rabe: Thinly chop the stems, then roughly chop once you reach the leaves. Wash and dry in a salad spinner. Add to a 9x13-inch baking dish. Repeat with the remaining bunch—this will look preposterous, but just trust, it’ll cook down in the oven.
Stir together the cream, salt, and pepper. Taste and adjust if needed. Slowly, evenly pour the cream on top of the broccoli rabe. Sprinkle the grated cheese all over.
Transfer the whole baking dish to a sheet pan (this will catch any spills mid-bake). Bake for 60 to 75 minutes, until the cheese is beginning to blister and brown, the broccoli rabe is tender throughout and crispy on top, and the cream has thickened slightly.