1. For the sauce: Whisk all ingredients together in a large bowl until combined. Set aside.
2. For the shrimp and broccoli: Thinly slice bell pepper. Chop broccoli into small pieces. Peel and devein shrimp.
3. Add 1/2 of the olive oil to a large skillet set over medium-high heat. Add bell pepper and broccoli and season with salt and black pepper, to taste.
4. Quickly stir fry the vegetables just until crisp tender and nicely browned, approximately 3-4 minutes. Transfer vegetables to a bowl and set aside.
5. Reduce heat to medium and add remaining olive oil to skillet. Add shrimp to the skillet and spread into a single layer without overcrowding.
6. Season with salt and black pepper, to taste. Cook, stirring once, just until the shrimp is opaque and starts to curl, approximately 2 minutes. Do not overcook.
7. Transfer shrimp to the bowl with sautéed vegetables. Set aside.
8. Create a slurry by combining the cornstarch and water together in a small bowl.
9. Add sauce and slurry to skillet and cook, stirring frequently, until the sauce thickens and clings to a spoon, approximately 2-3 minutes.
10. Remove from heat and pour shrimp and sautéed vegetables into the skillet.
11. Carefully toss to combine and garnish with sesame seeds and/or crushed red pepper flakes, if desired, before serving.