Trim the tough ends off the asparagus (about 1–2 inches from the bottom). Cut the asparagus into 2-inch pieces. Slice the mushrooms.
Sauté the asparagus:
Heat the olive oil (or butter) in a large skillet over medium heat. Add the asparagus pieces and sauté for 3-4 minutes until they start to become tender but still have a slight crunch. You want the asparagus to remain bright green and slightly crispy.
Add the mushrooms:
Add the sliced mushrooms to the pan with the asparagus. Cook for another 5-7 minutes, stirring occasionally, until the mushrooms release their moisture and become golden brown.
Season and flavor:
Add the minced garlic, fresh thyme (or dried), and red pepper flakes (if using). Cook for another 1-2 minutes, until the garlic is fragrant and the asparagus is tender. Season with salt and pepper to taste.
Finish with lemon:
Drizzle the lemon juice over the vegetables, giving them a final stir to coat everything evenly.
Serve:
Transfer the sautéed asparagus and mushrooms to a serving dish. Garnish with fresh parsley if desired, and serve warm.
