Fajita skillet sauce is generally sold in a liquid pouch instead of a dried packet. (We've tested this recipe with Frontera and Ortega skillet sauces, and both turned out well with different flavors. Be sure to use one you love!) We love skillet sauces and always have some on-hand, but we don't always have the time to watch the skillet. If you don’t have a skillet sauce on-hand, you can use a 1-ounce package of fajita spice mix layered on top of the peppers. Then after pressure cooking, use just 2 tablespoons of cornstarch and water to thicken.