Preheat oven to 350 degrees Fahrenheit. Prepare a metal cookie sheet with parchment paper.
In a stand mixer fitted with a paddle attachment. Cream together softened butter, sugar, and salt for 3 minutes until light and fluffy.
Scrape down the sides of the bowl, add in egg and vanilla, then mix until combined.
Mix in flour until a soft dough forms. This doesn't take long. The dough should be able to be shaped right away from the bowl, but if the dough seems to sticky (especially if you live in a warmer climate), you can refrigerate/chill the dough for 15-30 minutes to firm up.
Roll dough into 1" balls. These cookies are meant to be a little smaller but you can make them bigger. Just keep in mind that you will get less. I like to use a cookie scoop to help measure the dough and create consistently sized cookies.
Roll each ball into the extra 2 tablespoons of granulated sugar. Set on a prepared baking sheet. Take a small melon baller or your thumb (hence the name!) and make an even circle indent into each cookie.
Scoop or pipe in your jam of choice filling the indent. I like to put the jam in a piping bag or Ziploc bag with a snipped end to make filling the indents on the cookies quickly, easily, and without mess!
Bake cookies for 14-16 minutes. Cookies should still be very light and color. Do not overbake! 14 minutes is perfect for my convection oven.
Let cookies cool completely. Melt white chocolate chips and drizzle over top of the cookies and enjoy!