Autumn/Winter Frittata Recipe - Vegetarian Swiss Cuisine

Ingredients

• 2-3 tbsp olive oil
• 1 tbsp butter
• 1 medium-sized onion , peeled and sliced
• 1 tsp salt
• 2 large stalks ruby chard
• 2 medium-sized potatoes , scrubbed, unpeeled and thinly sliced
• 2 tsp dried rosemary
• 0.5 tsp dried sage
• 2 tsp minced garlic
• 8 large eggs
• freshly ground black pepper
• 1 cup diced gruyère cheese