Combine barley and water in a bowl. Let stand for 2 hours; drain.
Bring Rich Porcini Stock to a simmer in a saucepan. Heat oil in a Dutch oven over medium heat. Add onion; cook 5 minutes or until tender. Add mushrooms and salt; cook 3 minutes.
Add barley, Rich Porcini Stock, and sage to the onion mixture. Bring to a boil over medium heat; reduce heat, and simmer 30 minutes or until most of the liquid is absorbed. Remove from heat; stir in cheese, butter, and pepper.