Slow Cooker Butter Chicken

• 1 kg chicken thigh fillets
• 1 large brown onion, diced
• 2 cloves garlic, crushed
• 312 g Butter Chicken curry paste
• 2 tbsp tomato paste
• 400 ml tin coconut milk
• 100 g plain Greek yoghurt
• 200 g snow peas
• 450 g steamed brown rice