Prepare all the vegetables for this dish by washing, peeling, and cutting them according to the recipe. (Keep the vegetables separate since they will be added to the skillet at different times.)
Heat a large skillet over medium-high heat. Once the skillet is hot, add the butter and minced garlic. Sauté for 30 seconds to 1 minute, until the butter melts and the garlic is fragrant.
3 Tbsp unsalted butter, 3 garlic cloves, minced
Add the diced onions, halved mushrooms, and carrot strips to the skillet and sauté for 3–4 minutes, until the vegetables begin to soften. Stir occasionally to keep the vegetables from burning.
1/2 red or yellow onion, largely diced (1-inch squares), 3 medium carrots, peeled & thinly sliced into 2-inch strips, 8 oz white or portobello mushrooms, halved
As the vegetables cook, season with salt and pepper to taste. (Be careful not to over-season since the sauce will add plenty of flavor.)
1 medium zucchini, thinly sliced into 2-inch strips, 1 cup medium broccoli florets, 1/4 tsp salt, or to taste, ¼ tsp ground black pepper, or to taste
While the vegetables are sautéing, add all the sauce ingredients to a bowl or large measuring cup and whisk until well combined.
1/2 cup soy sauce, 1/4 cup water, 2 Tbsp brown sugar, 1 tsp sesame oil, 1 Tbsp cornstarch
Once the vegetables begin to soften, add the broccoli and zucchini to the skillet and pour in the sauce. Stir to coat all the vegetables in the sauce. Continue cooking over medium-high heat until the sauce comes to a simmer and begins to thicken, about 2–3 minutes.
Once the sauce is thick and bubbly and the vegetables are tender, remove the skillet from the heat. Top with freshly chopped green onions and sesame seeds and serve immediately with your desired sides.