Autumn Frittata - Potato Nation

Ingredients

• 300 ml chicken stock
• 500 g potatoes, peeled and quartered
• 45 ml (3 tbsp) olive oil
• 1 onion, finely chopped
• 3 celery sticks, sliced
• 120 g spinach, washed
• 6 large eggs, lightly beaten
• Salt and freshly ground black pepper, to taste
• 100 g Parmesan, freshly grated