Combine the flour, sugar, and salt in a food processor. “Sift” by pulsing the machine once. Scatter the butter bits on top of the flour and pulse 5 or 6 times, until the butter is the size of small peas.
In a small bowl, lightly beat the egg. Blend in the cream and vanilla. Add to the dough and process for 5 seconds; dump onto a sheet of waxed paper. Break off nug