I'd like to make a lasagna with mushrooms finely chopped and cooked with some Italian sausage to make the base for the meat sauce. However, all I have are Portobello Mushrooms. Will they work for this?
The simple answer is Yes. Of course you can use Portobello in your lasagna. You can dice them up and add them to your sauce, no problem at all.
If that is the end product you want then you should make it that way but I would recommend slicing the Portobello into long thin slices. This will accentuate the lovely texture of the Portobello and you could add a nice layering effect to an already nicely layered dish.
Be sure with whatever method you use you cook them quickly on high heat with a little Salt and Pepper to help bring out their flavor.