From The Big Orange Book by Rachael Ray [this is slightly different...you don't broil it and it seems to be slightly larger, but same general idea]
1 pound pasta [she used cavatappi, I just used what I had]
2 tbsp oil
2 large onions, thinly sliced
black pepper and salt
3 tbsp butter
3 tbsp flour
3 cups milk
2 cups shredded provolone [I bought a bulk and shredded it myself - you can't buy pre-shredded where I am]
1/2 cup beef stock
3/4 pound deli roast beef, thinkly sliced and coarsely chopped
1/4 cup fresh flat-leaf parsley
Place a large pot of salted water over high heat and bring it to a boil.
Once the water boils, cook the pasta according to package directions. Once the pasta has finished cooking, drain it and return it to the pot it was cooked in.
While the pasta is cooking, place a large skillet over medium-high heat the oil. Add the onions to the pan and season with salt and pepper and top them with a lid or piece of aluminum foil for 2-3 minutes, just to get them cooking. Remove the lid or aluminum foil and continue cooking the onions until tender and lightly caramelized,12-15 minutes, stirring occasionally.
While the onions are caramelizing, melt the butter over medium-high heat in a medium-size pot. Sprinkle the flour over the melted butter and cook the mixture for about 1 minute. Whisk the milk into the butter-flour mixture slowly and bring up to a bubble to thicken. Remove the pot from the heat and stir in 1 1/2 cups shredded cheese. Season with salt and freshly ground black pepper and reserve.
Preheat the broiler.
To the skillet with the onions, add the beef stock and the roast beef. Cook to warm through.
Add cheese sauce and onion-roast mixture to the pot with the drained poasta and toss to combine. Put in a 9 by 13 casserole dish and top with remaining cheese. [her cheese doesn't add up in the book...the online recipe is slightly different...I used 1 1/2 in the sauce and then just coated the top of the casserole.] Place under broiler until bubble, 2-3 minmutes.
Garnish with parsley.
Serves 6 [more like 12...I halved this and still got at least six servings].