In large sauce pan (I used my dutch oven), add butter and mushrooms.  Sprinkle with salt and cook until juices have released and are done.  Remove from pan and reserve for later.

In same pan over medium heat, add 2 tbsp oil.  Add rice and stir until rice is coated with oil.  Cook and stir for 2-4 minutes until just before rice starts to brown.  

Add 1/2 cup white wine. Stir constantly until completely absorbed.  

Add 1/2 cup broth, stir completely until absorbed and rice is starting to seem dry.  Add 1/2 cup broth at a time, stirring constantly and allowing broth to absorb completely before adding more.  When 4 cups have been added, taste for doneness. Rice should be creamy and cooked to al dente.  It should have just a little firmness to it.

Stir in mushrooms with any liquid that is with them.  Stir in peas. Taste for salt and stir in additional salt if needed.

Stir in cheese if desired.  

This can be used as a complete vegetarian meal or as a side to another dish.  We served it with our Pan Seared Scallops and Caper Sauce.