In a saucepan, melt butter over low heat, then set aside to cool for at least five minutes.
Then add egg and yolk, one at a time, mixing after each addition. Add in vanilla and mix until combined.
In a separate bowl, combine flour, baking soda and salt.
Add half of the dry ingredients to the wet ingredients, and stir by hand to combine. Add remaining dry ingredients, and stir to combine, but do not overmix.