Wash, trim, and slice the Brussels into 1/4 to 1/2 inch rounds. Dice the onion fine, and mince the garlic separately. Prepare the gnocchi dough before proceeding.

Heat olive oil and butter in a large skillet over medium heat. Add Brussels sprouts and onion; cook and stir until onion starts to turn translucent, about 5 minutes. Stir in garlic, salt, and pepper.

Cook the gnocchi at the same time as the Brussels mixture. Drain the gnocchi and toss with a small amount of oil if they are done ahead of the brussels.

Increase the brussels' heat to medium-high; cook and stir gnocchi until are browned, 2 to 3 minutes. Stir in lemon juice, red pepper flakes, and parmesan cheese, as desired.