Prep the tempeh: Cut the tempeh into bite-size pieces. If you’re sensitive to tempeh’s slight bitterness, steam it for 10 minutes or microwave with a splash of water for 1–2 minutes.
Pat dry.
Mix the sauce: In a small bowl, whisk soy sauce, rice vinegar, maple syrup, cornstarch, and water. Add miso or hoisin if using. Set aside.
Heat the pan: Place a large skillet or wok over medium-high heat.
Add 1–2 tablespoons oil and swirl to coat.
Crisp the tempeh: Add the tempeh in a single layer. Cook 3–4 minutes per side until golden and lightly crisp. Remove to a plate.
Quick-cook the broccoli: Add another splash of oil if the pan looks dry.
Toss in broccoli florets and sliced stems. Stir-fry 2–3 minutes. Add a splash of water, cover for 1 minute to steam until crisp-tender.
Add aromatics: Uncover, push broccoli to the edges, and add garlic, ginger, and the white parts of the green onions to the center.
Cook 30–45 seconds until fragrant.
Combine and sauce: Return tempeh to the pan. Stir the sauce again to re-disperse the cornstarch, then pour it in. Toss everything to coat as the sauce thickens and turns glossy, about 1–2 minutes.
Finish: Turn off the heat.
Stir in toasted sesame oil and red pepper flakes or chili-garlic sauce if you like it spicy. Sprinkle with green onion tops and sesame seeds.
Serve: Spoon over warm rice or toss with noodles. Taste and adjust with a splash more soy or vinegar if needed.