Step 1. Melt a third of the butter in a large non stick frying pan over medium high heat. Add the mushrooms, onion, harissa paste and garlic; cook for 3 minutes, stirring occasionally, or until browned and caramelised. Remove mushroom mixture and set aside.

Step 2. Combine ricotta, tasty cheese and lemon rind in a small bowl; season.

Step 3. Spread cheese mixture onto two slices of bread. Top with the mushroom mixture and spinach; cap with remaining bread slices. Spread another third of the butter on the top bread slices.

Step 4. Melt remaining butter in same clean pan over medium low heat. Add sandwiches, buttered side up to the pan. Cook for 2 minutes each side or until golden brown and cheese is melted. Cut toasties in half, to serve.