Photo: Andrew Montgomery
Preheat the oven to 200°C/fan 180°C/gas mark 6. Trim off the woody ends of the asparagus. Bring a pan of water to the boil, then add the asparagus and cook for 4-5 minutes until just tender. Tip into a colander and run under the cold tap. Leave to drain.
Heat the oil in a small frying pan. Add the spring onions and a pinch of salt and cook for 5 minutes until soft and sweet. Set aside.
Unroll the pastry and put it on a large baking sheet. Use the tip of a knife to score a line all the way around 1½cm in from the edge to form a rim for the tart. Don't cut all the way through. Prick the centre with a fork, then hold a sharp knife horizontally against the cut edge of the pastry and gently tap the edge all the way round to separate the layers. Cook for 20 minutes, then remove from the oven and press down the centre, leaving a raised rim around the outside.
Meanwhile, beat together the cream, eggs and grated parmesan with the garlic and some seasoning. Add the chopped mint and cooked spring onions.
When the pastry is ready, turn the oven down to 160°C/fan 140°C/gas mark 3. Pour the filling into the prepared pastry case. Arrange the asparagus tightly in lines on top and splash with olive oil. Bake the tart for 25-30 minutes, or until the top has puffed up a little. Drizzle 1 tbsp extra-virgin olive oil over the top and leave to cool for a few minutes. Scatter with the mint leaves and cut into slices to serve.