I knew I had to use cheese with an edge since I was cutting Gruyere which has a twang to it. I decided to go for body and creaminess instead - so I went with a hot pepper cheese and a smoked Gouda. Very good decision when paired with the sweet onion mixture.
The second thing I am quite happy about is my decision to use a very very small pasta - one I'd typically throw into an Italian soup. Not orzo or anything - you still need a little bite. The cheese sauce permeated every single nook and cranny and I noticed I didn't have to use as much sauce to get a cheesy flavor. HUGE money saver because you can literally make double!
To start, slice 1 large onion and 3 cloves of chopped garlic and start frying it on medium heat.
Let it caramelize low and slow and then add 1/2 tsp sage, sprinkle of salt, pepper, 1/4 - 1/2 cup of cooking sherry, and about 1/2 cup of beef stock. Let this cook down, then add another 1/2 cup of beef stock or enough to thin it out. Stir in about 1/2 tsp of cornstarch to thicken the mixture and set aside after it looks like the picture below.
Then start on the cheese sauce by melting 2 Tbs of butter and 1/4 cups of flour. Whisk together for a few seconds, then add 2 cups of milk - maybe even 3. Stir until thickened - it will look runny and then all of a sudden come together. Stir in your cheese (turn the heat down to medium low). I used a whole package of both cheeses, so it made a lot (about 2 1/2 cups of cheese total). Whisk until creamy, then add a good couple of squeezes of Dijon mustard.
Add the onions and store half in a container (I freeze this so I have more later) and mix the rest in with your pasta. I like creamy mac and cheese, so this is where I ended the show. But you can always cover with a little butter/breadcrumb mixture and bake at 350 for about 20 minutes.