Measure all of your seasonings, the onion powder, the oregano, the pepper, the basil, and the parsley into a small bowl.
In a large skillet, brown the Italian seasoning, if you are using it, and chop it into small bits with a spatula. When the meat is cooked, drain the fat from the meat and then set the meat aside in a bowl.
As you cook the Italian sausage, bring a Dutch oven of water and a teaspoon of salt to a boil over medium high heat.
Melt the butter in the skillet in which you cooked the meat over medium heat. Add the garlic and cook it in the butter. Let the butter cook until it is a golden brown color. Add the olive oil.
Stir the flour into the hot oil and use your spatula to stir it all up into a paste. Cook these together for about two minutes.
Add the chicken broth and the half and half, using a whisk to stir the ingredients together. Stir in the seasonings. Continue whisking to avoid lumps and scorching. Bring the liquid to a boil and then reduce the heat, whisking frequently. Simmer the sauce for about 5 minutes.
By now, the Dutch oven of water should be boiling. Add the tortellini to the boiling water and cook it according to the time specified on the package. Drain the tortellini in a colander.
Turn the sauce to low heat and add the Asiago cheese and Parmesan cheese. Stir the sauce well to incorporate the cheeses and let them melt. Taste the sauce and add pepper and salt if you think it needs it.
Add the meat, if you are using meat, and the drained tortellini and toss with a wooden spoon to coat the pasta in the sauce.
Serve the pasta hot. Store leftovers in the refrigerator for up to three days. To reheat, you will need to add a couple of tablespoons of milk to the mixture before you microwave your serving for about 45 seconds.