Heat the oil: In a large skillet over medium heat, warm olive oil (or butter).
Sauté the garlic: Add minced garlic and cook for 30 seconds until fragrant. Stir frequently to prevent burning.
Add mushrooms: Stir in the sliced mushrooms. Cook undisturbed for 3–4 minutes so they brown, then stir and cook another 3–4 minutes until tender.
Add cauliflower: Toss in the cauliflower florets. Season with salt, pepper, thyme, and optional red pepper flakes.
Steam to soften: Add ¼ cup broth or water, cover the skillet with a lid, and let steam for 8–10 minutes until the cauliflower is tender-crisp.
Uncover and reduce liquid: Remove the lid and cook for another 2–3 minutes if any excess moisture remains.
Finish the dish: Add lemon juice and chopped parsley. Stir everything well and adjust seasoning to taste.
Serve warm: Enjoy immediately as a main or side dish.