Heat olive oil and 1 tablespoon of butter in a large skillet over medium-high heat.
Add the cauliflower florets to the skillet and sauté for 5 to 7 minutes until they begin to soften and brown slightly.
Push the cauliflower to the perimeter of the skillet and add the remaining tablespoon of butter to the center.
Add the sliced mushrooms to the center and cook for 4 to 5 minutes until browned and moisture has evaporated.
Stir the mushrooms and cauliflower together, then add the minced garlic, salt, and pepper.
Sauté for an additional 2 minutes until the garlic is fragrant and cauliflower is tender.
Remove from heat, stir in the fresh parsley and lemon juice, and serve immediately.