Start by making the pastry in advance. Pass the flour through a fine sieve, beat the butter and the egg to make sure it is all uniform and start kneading flour, egg and butter together. Once combined, add the grated Grana Padano and keep kneading until smooth. Let it rest in the fridge for at least 30 minutes, wrapped in cling film as it is best to work the pastry when colder. With the help of a rolling pin, flattened the pastry until you have a 1 cm thin round sheet. You can do this operation between to sheets of baking parchment to avoid any pastry to stick to the table. Choose a cake tin large enough for 6 (26 cm Ø) and line it with parchment and carefully let the pasty slide in. Make sure all edges are at least 3/4 cm high. Rolling the pastry onto the rolling pin could be helpful in this process to move it and let it fall into the tin. With a paring knife remove the excess of pastry if you have any to be use later as decorative strips. Let the base set well in the fridge.
Prepare the wheat base. Simmer the grains with the milk and butter for about 10 minutes and mix it every now and then and let it cool once ready. The liquid should be absorbed and the texture quite firm. Now combine the mixture with the ricotta, the Grana Padano, the chopped asparagus (save some tips as garnish if you want), 1 egg and season with a pinch of salt and pepper. The filling should look like a chunky custard so if the result is too hard, add a splash of milk. Pour the filling into the cake base until around 2.5 cm high (just below the edge you have cut) and decorate with the remaining pastry creating the classic ‘Italian crostata’ strips pattern on the top of the pie. Add the asparagus tips as in the picture and brush with the egg wash.
Now bake the pie at about 160 (with the oven fan half power if you have) for about 45/50 minutes or until well golden. Check if the filling is firm and set before taking it out of the oven. If it is still a bit runny, lower the temperature by 10 degrees and keep cooking for 5 more minutes until ready.
Sprinkle with some extra Grana Padano cheese and serve with a side of rocket salad if you wish. This Pastiera is great at room temperature or even better reheated to a warm temperature. You can keep the pie for a couple of days out of the fridge and up to a week inside.