French Butter Cookies

Instructions

1. Prepare the dough
   In a large bowl, cream together the softened butter and sugar until light and fluffy, about 3 minutes. Add the egg yolks one at a time, mixing well after each addition. Stir in the vanilla extract and lemon zest if using.
2. Add dry ingredients
   In a separate bowl, whisk together the flour and salt. Gradually add the flour mixture to the butter mixture, mixing on low speed until just combined. Do not overmix or the cookies will be tough.
3. Chill the dough
   Divide the dough in half and shape each half into a log about 2 inches (5 cm) in diameter. Wrap each log in plastic wrap and refrigerate for at least 1 hour, or up to 3 days. This allows the flavors to develop and makes the dough easier to slice.
4. Prepare for baking
   Preheat the oven to 350°F (175°C). Line two baking sheets with parchment paper. Remove one log from the refrigerator and let it sit at room temperature for 5-10 minutes to soften slightly.
5. Slice and decorate
   Using a sharp knife, cut the log into rounds about 1/4 inch (6 mm) thick. Place the rounds on the prepared baking sheets, leaving about 1 inch (2.5 cm) between each cookie. Lightly brush the tops with beaten egg and sprinkle with turbinado sugar if desired.
6. Bake to perfection
   Bake for 12-15 minutes, until the edges are lightly golden but the centers are still pale. Be careful not to overbake, as these cookies should remain pale. Remove from the oven and let cool on the baking sheets for 5 minutes before transferring to a wire rack to cool completely.