Add butter and sugars to a large bowl. Using a mixer, cream butter and sugars until combined.
Turn mixer on low. Add egg, mixing completely. Mix in vanilla extract, salt, and baking soda.
Add flou to the wet ingredients and mix until combined.
Add Kit Kats and white chocolate chips. NOTE: if you’re not using a stand mixer, chop your Kit Kats smaller. If you are using a stand mixer, run it on medium-low speed for about 15 seconds. The Kit Kats will break up smaller during mixing.
Scoop 2 tablespoon size cookie balls onto a cookie sheet lined with parchment or a silpat liner. Chill at least 1 hour before baking.
Preheat oven to 350°. Line an additional cookie sheet with parchment or a silpat liner. Separate cookie balls 2-inches apart.
Bake for 12-15 minutes, or until lightly golden around the edges and no longer glossy. It's important not to over bake these. When they come out of the oven you can press some more Kit Kat pieces on the top to make them prettier, if you want. Cool at least 5 minutes on cookie sheets.
Store in an airtight container for up to 4 days or freeze for up to 3 months.