1. In the slow cooker, combine the rice, butter, onions, soup, 1 teaspoon of the salt, and the pepper. Mix well.
2. Lay the sliced mushrooms on top of the ingredients in the slow cooker. Push down lightly. This helps keep all the rice under the liquid and allows the mushrooms to cook at a bit of a slower pace.
3. Cook on low 6 to 8 hours or for 3 hours on high.
4. Uncover and fluff to incorporate the mushrooms. Add up to 1 teaspoon of the remaining salt, to taste. All done.
Alternatively, you can use your favorite vegan mushroom soup. If it is condensed, make at least 16 ounces of the soup, then add enough water or vegetable stock to make 32 ounces.
Although this soup seems to need the full 2 teaspoons of salt to balance the flavors, you may prefer to add only 1 teaspoon prior to cooking; taste and add more afterward, if desired.
Storing in the refrigerator
After cooking and cooling, this will also keep in the refrigerator for up to 3 days.
After cooling, you can keep in the freezer in either freezer bags or hard-sided containers for up to 3 months. To prepare after freezing, defrost in the refrigerator for 3 to 4 hours.
Place in a microwave-safe bowl and microwave on high power for 3 minutes, stirring every 45 seconds. Check that it's hot enough.