Leftover sauce? I wish I had that problem. No matter how much sauce I put in a lasagna, it seems to soak it all up while it’s baking and I wind up with a lasagna that’s meaty and cheesy, but not saucy.
You can use it as a dipping sauce for those finger food sort of nights. cheese sticks, good breads or crackers, jalapeño poppers, etc. A lot of restaurants serve a marina as a dipping sauce for all sorts of appetizers.
Tortelloni. Err on the side of bigger, make a sage sauce with a butter and reduced white wine emulsion and sprinkle generously with cheese.
If you have too much tortelloni you can freeze them.
have a small pot of heated sauce separate from the lasagna and add a ladle full to each piece after you plate it, along with a little extra fresh grated parmigiano reggiano. This is standard practice for us. Doesn’t everyone do this?