Melt-in-the-middle Leerdammer stuffed mushrooms

Ingredients

• 0 100g quinoa
• 0 1 bay leaf
• 0 Zest and juice of ½ lemon
• 0 2 spring onions
• 0 1 stick of celery, very finely chopped
• 0 1 green chili, deseeded and finely chopped
• 0 Tbsp pumpkin seeds, popped in a dry frying pan
• 0 A handful of flat leaf parsley, chopped
• 0 Tbsp olive oil
• 0 2 tsp sherry vinegar
• 0 4 slices Leerdammer
• 0 4-6 large field, closed cup or breakfast mushrooms
• 0 40g unsalted butter, at room temperature
• 0 2 cloves garlic, minced
• 0 ½ tsp freshly ground black pepper