Heat the 2 tablespoons olive oil in a small sauce pan and add the garlic. Cook over medium heat about 4-5 minutes until the garlic is fragrant, but not yet browned. Set aside.
Zest the lemon into a medium-sized serving bowl. Then cut it in half and squeeze all its juice into the same bowl. Avoid getting the seeds into the mixture. Set aside.
Clean and slice the mushrooms vertically through the caps into 1/4-inch thick slices. Set aside.
Place the broccoli florets in to a microwave proof bowl and cover it with plastic wrap. Microwave, on high, about 2-3 minutes (depending on your microwave), until the broccoli is bright green and tender crisp. Remove the plastic wrap and run cool water into the bowl, empty and repeat several times to stop the cooking quickly.
Using a salad spinner dry the florets as well as possible and add them to the serving bowl with the lemon mixture. Follow this with the garlic pieces and all its oil. Toss the mixture well. Refrigerate until cold and ready to serve.
To serve toss the broccoli salad with the reserved mushroom slices and divide the salad evenly among 4 plates. Garnish with Parmesan cheese and a drizzle of olive oil.