12 | medium-size | Mushroom caps |
1 | tbsp | Olive oil |
1 | tbsp | Sweet butter |
1/2 | C | Finely chopped yellow onion |
2 | tbsp | Coarsely chopped walnuts |
1 | Garlic clove, peeled and minced | |
5 | oz | Frozen spinach, thoroughly defrosted and squeezed dry |
1 | oz | Feta cheese, crumbled |
1 | oz | Gruyere cheese, crumbled |
2 | tbsp | Minced fresh dill |
Salt and freshly ground black pepper to taste |