Heat oil in a medium sauté pan over medium heat. Add onions, bell pepper, celery, and garlic and sauté until translucent. Add tomatoes and stock.In a separate dish, mix the cornstarch with cold water.Stir cornstarch slurry into pan and reduce heat to medium low. Season with salt and as much hot sauce as you can handle! (Add sauce a few drops at a time, tasting along the way and adding more if needed.) Chef Guas pairs this hot sauce on his Spicy Crawfish Tamales.