Press the tempeh to remove excess moisture, then slice into 1/4-inch thick pieces.
In a shallow dish, marinate tempeh with half the minced garlic, lemon juice, salt, and pepper. Let it sit for at least 15 minutes.
Preheat a grill pan over medium-high heat. Grill the tempeh slices for about 3-4 minutes per side until grill marks form and the pieces are heated through.
While the tempeh is grilling, steam the green beans in a steamer or skillet with a splash of water until they are tender-crisp, about 5-6 minutes. In the last minute, toss with a little minced garlic, salt, and pepper.
For the cauliflower mash, steam the cauliflower florets until soft, about 10 minutes. Transfer to a food processor, add the remaining garlic, olive oil, salt, and pepper, and blend until smooth. Adjust seasoning if needed.
Plate the grilled tempeh alongside a serving of garlic green beans and a generous scoop of cauliflower mash.
Garnish with an extra drizzle of olive oil or a squeeze of lemon if desired, and serve warm.