Instant rice has already been cooked and dehydrated. It only takes a few minutes to prepare, but the flavor is bland.
Converted or parboiled rice, such as Uncle Ben's, has been soaked, pressure steamed and dried. It takes a little longer to cook than regular rice.
The recipe for Mushroom Rice Casserole uses long grain rice and five other ingredients: butter or margarine, mushrooms, onion, cream of mushroom soup and beef consomme. Unlike a lot of recipes, the rice doesn't have to be cooked ahead of time. It's sauteed with the mushrooms and onion, but only long enough for the rice to soften. All the ingredients are mixed together, put in a casserole dish and baked for an hour.
I always use margarine and 98% fat-free soup. You can use regular soup if you prefer, but I don't recommend using butter to saute the ingredients. Butter burns easier than margarine, unless you use clarified butter.
Clarified butter is butter that's been melted at a low temperature. The fat rises and the milk solids sink. The clear liquid left in the middle is clarified butter. It has a higher smoking point which makes it better for sauteing food at a high temperature.
I love to serve Mushroom Rice Casserole with Marinated Baked Chicken. Not only do the dishes complement each other, they can be baked at the same temperature and for the same length of time. The casserole is also good with Baked Salmon Patties. If you want to serve it with the salmon patties, put the rice in to cook 15 minutes before the salmon.