Mushroom Onion Barley Risotto

1 tbsp organic butter or extra virgin olive oil    
2 cups sliced portobello mushrooms
1 small onion, chopped                    
1/2 tsp dried thyme
1 cup pearl barley, rinsed                    
2 1/2 cups low-sodium vegetable stock
1/3 cup finely chopped walnuts        
1/4 cup grated Grana Padano imported Parmigiano cheese
2 tbsp chopped fresh parsley
Celtic sea salt and freshly-ground black pepper

In a medium saucepan, heat butter or oil over medium heat. Add mushrooms, onion and thyme; cook, stirring, for 5 minutes or until softened.  Stir in barley and stock; bring to a boil. Reduce heat, cover and simmer, stirring occasionally and adding more stock if necessary, for 30 minutes or until barley is tender.  Stir in walnuts, cheese and parsley; season with Celtic salt and pepper to taste.