In a pan add 1 Tbsp olive oil and fry the onions and aubergine until slightly browned, 2-3 minutes.
Add them into the slow cooker along with the garlic, stock, vinegar, chilli, olives, capers, pine nuts and chopped tomatoes. Use one of the empty cans to add a can of boiling water. Cook on high for 3 hours.
Add the orzo and cook for an additional 30 minutes.
At the end stir in a handful of fresh parsley and season with salt and pepper to taste.