Charred spring onion and ricotta tart

Name: Charred spring onion and ricotta tart
Prep time: 20 min
Total time: 20 min
Cuisine: European, British
Ingredients: 300g spring onions (about 3 bunches), ends trimmed and outer layers removed; 1 tbsp olive oil; 1 x 320g sheet ready rolled puff pastry; 1 x 250g tub ricotta - use vegetarian cheese if required; 75g Gruyère*, grated finely - use vegetarian cheese if required; ½ x 20g pack tarragon, chopped; zest and juice of ½ lemon; 30g blanched hazelnuts, roughly chopped; 1 tbsp clear honey