In a medium bowl, season the beef strips with salt, black pepper, smoked paprika, and dried thyme. Set aside.
Heat 1 tablespoon of olive oil in a large skillet over medium-high heat. Add the beef strips and sear for 3-4 minutes until browned but not fully cooked. Remove beef from skillet and set aside.
In the same skillet, add the remaining 1 tablespoon of olive oil. Add the diced onion and minced garlic, sauté for 2 minutes until fragrant and translucent.
Add the chicken pieces to the skillet and cook for 5-6 minutes until they start to brown and are cooked through.
Add the sliced red and green bell peppers and mushrooms to the skillet. Cook for 4-5 minutes until the vegetables are tender.
Return the seared beef strips to the skillet with the chicken and vegetables. Stir to combine.
In a small bowl, whisk together the beef broth, chicken broth, soy sauce, cornstarch, and cold water until smooth.
Pour the broth mixture into the skillet and stir well. Cook for 3-4 minutes, stirring occasionally, until the sauce thickens and coats the meat and vegetables.
Remove from heat and garnish with chopped fresh parsley before serving.