In a medium bowl, whisk sour cream and sriracha until smooth. If needed, add water, a few drops a time, until sauce is a good consistency for drizzling. Refrigerate until ready to use. In another medium bowl, whisk brown sugar, soy sauce, cornstarch, vinegar, sesame oil, and 1/2 cup water until smooth. Let sit at room temperature until ready to use. Cut your green onions.

In a large nonstick skillet or wok over high heat, heat vegetable oil. Cook garlic and green onion, stirring frequently, until light golden, about 1 minute. Add beef and cook, breaking up into smaller pieces, until just cooked through and starting to brown, about 5 minutes. Drain excess oil.

Add broccoli and cook, stirring frequently, until bright-green, about 2 minutes. Add carrots and reserved soy sauce mixture. Cook, stirring frequently, until sauce thickens and vegetables are crisp-tender, 3 to 4 minutes more.

It should look like this when done. Best served over white rice. Drizzle sauce over & sprinkle sesame seeds on top.