Put the yogurt, 6 tablespoons of the olive oil, the garlic, and ⅔ cup of the peas in a food processor. Blitz to a uniform pale green sauce and transfer to a large mixing bowl.
Cook the pasta in plenty of salted boiling water until al dente. As the pasta cooks, heat the remaining olive oil in a small frying pan over medium heat. Add the pine nuts and chile flakes and fry for 4 minutes, until the nuts are golden and the oil is deep red. Also, heat the remaining peas in some boiling water, then drain.
Drain the cooked pasta into a colander, shake well to get rid of the water, and add the pasta gradually to the yogurt sauce; adding it all at once may cause the yogurt to split. Add the warm peas, basil, feta, 1 teaspoon salt, and ½ teaspoon white pepper. Toss gently, transfer to individual bowls, and spoon over the pine nuts and their oil.
