Vegetarian stuffed peppers with rice and feta

Ingredients

• 4 bell peppers
• 1 cup basmati rice
• 5.6 oz feta cheese
• 4 tbsp olive oil
• 1 onion
• 2 cloves garlic
• 0.7 oz mint
• 0.7 oz parsley
• 1 tbsp harissa
• 3 1/2 oz walnuts
• 14 oz canned whole peeled tomatoes
• 1 1/3 cups vegetable broth
• 1 cup full-fat Greek yogurt
• 1 tsp ground coriander
• salt
• pepper