Put the farro in a bowl, cover with cold water and leave to soak for 15 minutes. Carefully peel off and discard any stringy bits from the sides of the sugar snap peas.
Drain, then tip the farro into a saucepan. Cover with cold water and bring to the boil over a medium heat. Cook for 20 to 30 minutes, until the grains are soft. Go by texture rather than timing. Drain well and leave to cool. Wipe out the saucepan.
Put the saucepan back on the stove and bring plenty of salted water to the boil. Add the sugar snap and podded peas and cook for 2 to 3 minutes, until just cooked. Drain and quickly run under cold water for 30 seconds to stop them cooking and cool them down. Drain again, shaking off any water.
Spoon pesto in a mixing bowl, along with the lemon juice and 2 tablespoons of the oil. Add the drained farro, the sugar snap and podded peas, and stir until everything is combined. Loosely toss in the rocket. Season, to taste, with salt and pepper, then divide the salad between bowls. Drizzle with the rest of the oil and tear a few basil leaves over the top. Scatter with the lemon zest, plus a few shavings of Parmesan or pecorino, then finish with a grind of black pepper.