Place a medium pan over medium-high heat. Add 2 tsp. olive oil to hot pan. Add mushrooms and sauté, stirring often, until lightly browned, about 4-5 minutes. Add ½ cup water and beef base to pan and stir to combine. Cut open packages of osso buco and add meat and all juices in package to pan. Bring to a boil, cover with a lid or foil, and reduce heat to low. Cook for 10 minutes, turn meat, and cook for another 10-15 minutes, or until a minimum internal temperature of 165 degrees is reached.