In a small bowl, whisk together the dry ingredients: flour, salt, baking soda, and espresso powder.
In a large bowl of a stand mixer, beat the butter and both sugars together until light and fluffy, about 3 minutes. Add the vanilly, whole egg, and egg yolk and mix until combined and mixture is fluffy, another 2 minutes.
Gradually add the dry ingredients to the butter and sugar mixture, beating until combined. Using a wooden spoon, fold in the white chocolate chips. Cover the bowl with plastic wrap and chill the dough for 30 minutes.
About 10 minutes before you're going to bake the cookies, preheat the oven to 350 degrees. Line baking sheets with a silicone baking mat or parchment paper. Using a cookie scoop, place 1 tablespoon of cookie dough on prepared baking sheets.
Bake for 10-12 minutes. Cool cookies on baking sheet for about 10 minutes before removing to wire cooling racks.