Add your butter to a large glass bowl.

Dump the sucanat on top.

Cream these together until soft, fluffy, and light brown.

Add egg yolk.

Add vanilla, salt, and baking soda.

Stir together thoroughly.  Now, add flour.

Stir until a stiff, smooth dough forms.

Refrigerate for at least an hour (although I baked the first few without doing so, and they worked just fine -- the dough is just harder to work with).  Let it soften on the counter for about 10 minutes.  Roll it out as desired, then bake at 350 for 8 - 10 minutes.