Boil tortellini in a large pot of water according to package directions. Add the broccoli to the water during the last minute of cooking. Drain tortellini and broccoli and set aside.
In the same pot, heat olive oil over medium high heat. Add the cut up chicken breast, salt, and onion powder. Cook until slightly browned and cooked through, about 8 minutes. Remove from pot and set aside.
In the same pot over medium heat, add the butter, garlic, and flour, whisking until the mixture is lightly browned, about 3 minutes. Continue whisking and pour in the milk. Increase heat until milk lightly bubbles and sauce thickens. Lower the heat and stir in the cheeses until they melt. Add in the tortellini, broccoli, and chicken. Serve warm.