Chop the pecans, toast them lightly in a frying pan (watch them carefully), remove from heat, set aside.
Start heating your oven to 190 C / 375 F / Gas Mark 5.
In a good-sized bowl, use an electric hand-mixer to cream together the sugar, butter, egg yolk and vanilla until fluffy. Add the flour a bit at a time, and beat it in. Then add the crushed potato chips and the nuts, and fold them in by hand.
Roll pieces of the dough into 1 inch (2 ½ cm) balls; position the balls on an ungreased cookie sheet about 3 inches (7 ½ cm) apart from each other.
Put a handful or so of additional white sugar in a saucer. Press the flat bottom of a water glass or tumbler into the sugar, and use it to press the balls of dough out flat. Repeat pressing the bottom of the glass as often as needed to keep sugar on the bottom so that the dough won't stick to it.
Bake until golden brown, about 12 to 15 minutes. Let cool for a few minutes on the cookie sheet, then remove.
Measure so that you have ⅓ a cup of potato chips after crushing.