Combine and let stand until mushrooms are softened - about 20 minutes.
Remove mushrooms and squeeze dry with paper towel.
Reserve soaking liquid.
Dice mushrooms finely and reserve.
Heat butter and vegetable oil over medium heat.
Add vegetables and cook, stirring until tender but not browned, 5-10 minutes.
Increase heat slightly and add barley. Cook, stirring until lightly toasted, about 5 minutes.
Stir in the reserved diced mushrooms, soaking liquid and stock.
Bring to a boil, reduce heat and simmer partially covered until barley is tender, about 40 minutes.
Season with fresh dill, salt and black pepper.