Cut sirloin into strips 2" long, ½" thick and ½" wide. Set them side.
Heat butter with 1 tablespoon of oil in a 5-quart Dutch oven over medium heat. Add the onion, shallot and dried red peppers; cook 1 minute. Add the garlic; cook 4 minutes longer. Using a slotted spoon, transfer the mixture to a plate.
Add 2 tablespoons of oil to the same pot. Sauté the mushrooms until golden, about 5 minutes. Using a slotted spoon, transfer them to the plate with the onions. Add 2 more tablespoons of the oil to the same pot. Sauté the beef strips, _ at a time, over medium-high heat until browned on all sides. Transfer the beef to a separate plate.
Reduce heat to medium-low. Add the barley and rice, and stir well. Add the stock, scraping the sides and bottom of the pot with a wooden spoon. Add the reserved onion-mushroom mixture, and heat to boiling. Then reduce the heat and simmer, covered, over medium-low heat until the barley and rice are tender and almost all the liquid has been absorbed, about 35 minutes. Add sautéed beef strips and cook, tossing constantly, over medium heat until warmed through, about 5 minutes. Season with salt and pepper, then stir in the sage and parsley. Serves 4 to 6.