Portobello steaks and butter bean mash

Ingredients

• 8 medium to large portobello mushrooms , stems removed
• 10 garlic cloves, peeled
• 1 onion, peeled and cut into 6 wedges
• 1½ tbsp chili flakes
• 1 red chilli
• 4 tsp cumin seeds, roughly crushed in a pestle and mortar
• 1 tbsp coriander seeds, roughly crushed in a pestle and mortar
• 1 tbsp tomato paste
• 4 oz olive oil
• Butter bean mash:
• 1 × 1.5 lb jar of cooked large butter beans, drained (1 lb)
• 1½ tbsp lemon juice
• 1 tbsp olive oil
• Sea salt or kosher salt