Preheat the oven to 200°C (180°C fan) | 400°F | gas 6. Parboil the asparagus in a large saucepan of salted, boiling water until just tender to the tip of a knife, about 2-3 minutes.
Drain and refresh immediately in a bowl of iced water.
Heat the olive oil in a large frying pan set over a medium heat. Add the onion, pancetta, and a pinch of salt, sautéing until the onion is soft, about 6-7 minutes. Set off the heat to cool.
Roll out the pastry on a lightly floured surface into a 35 cm | 14" x 20 cm | 8" x 3/4 cm | 1/3" thick rectangle, trimming the edges with a sharp knife to create a neat edge.
Lift the pastry onto the lined baking tray and prick the base with a fork, leaving a 2 cm | 3/4" border all the way around. Gently create a raised border all the way around with your fingertips. Spread the pastry with the ricotta and then arrange the sweated onion and pancetta mixture on top in an even layer.
Trim the ends of the asparagus spears so that they measure about 8-9 cm | 3-3 1/2" in width. Arrange groups of eight spears in a checkerboard pattern on top, six squares in total, alternating green and white asparagus on each side; see the image for direction if needed.
Bake for 15 minutes. Remove from the oven and carefully crack the eggs onto each section of asparagus. Return to the oven until the pastry is fully cooked through and the eggs are set, about 10-15 minutes.
Remove from the oven and let cool for 5-10 minutes before serving with a garnish of salad cress.