Prick each potato a few times with a fork, place on a microwave-safe plate, and cover with a damp paper towel. Microwave on high until fork tender, 5-8 minutes. Carefully cut potatoes in half (or quarters if your potatoes are on the large side).
Heat olive oil in a large skillet over medium-high heat. Add garlic, and saute for 1-2 minutes, just until fragrant. Add broth or wine.
Add green beans, mushrooms, and potatoes. Sprinkle with salt and pepper, and stir to combine. Cover, and reduce heat to medium. Cook until green beans are tender but not too soft, 5-8 minutes.
Turn off heat, squeeze lemon juice over vegetables, and stir once more before serving.