1. Preheat the oven to 200°C.
2. Place the pastry rectangles on a greased baking sheet and carefully score lines 1cm away from the pastry edges with a sharp knife. Prick the inner rectangle with a fork and brush with beaten egg.
3. Spread a thin layer of pesto all over the base of the inner rectangle and top with shaved Parmigiano Reggiano cheese and small spoonfuls of mascarpone cheese.
4. Blanch the asparagus spears for 1 minute in boiling salted water, drain, and place 3 spears across each tart.
5. Sprinkle a little lemon zest and grated Parmigiano Reggiano over each tart and bake in the oven for 15-20 minutes until the pastry is golden brown and risen.
6. Serve the tarts with shaved Parmgiano Reggiano and freshly torn basil leaves.
Recipe courtesy of Parmigiano Reggiano.