Prepare the Chicken
Cut the chicken into cubes or thin slices. Season with salt and pepper, then toss with cornstarch for a light coating.

Prep the Vegetables
Slice the red bell pepper, shiitake mushrooms, and red onion. Peel and finely chop the garlic.

Cook the Chicken
Heat 1 tablespoon of vegetable oil in a large skillet over high heat. Add the chicken and sauté until fully cooked and lightly browned, about 9 minutes. Remove from the pan and set aside.

Mix the Sauce
In a small bowl, whisk together the soy sauce, rice vinegar, water, brown sugar, cornstarch, and sriracha. Set aside.

Cook the Shrimp
Add the shrimp to the same skillet. Sauté for about 2 minutes, until pink and opaque. Remove from the pan and set aside with the chicken.

Sauté the Vegetables
Add another tablespoon of oil to the pan. Stir-fry the red bell pepper, mushrooms, red onion, and garlic until softened and slightly browned, about 7-9 minutes.

Combine Everything
Return the chicken and shrimp (plus any juices) to the skillet. Add the baby spinach in batches, stirring until just wilted.

Add the Sauce
Whisk the sauce again and pour it into the skillet. Cook for about 2 minutes, stirring until the spinach is fully wilted and everything is evenly coated.

Serve
Serve hot over rice, noodles, or as is for a low-carb option!