Cream butter and sugars. Add egg, vanilla and mix. Add dry ingredients and mix. Fold in chocolate and pretzels. Form into balls, place on sheet and refrigerate for at least 20 minutes.
Place dough balls on a lined baking sheet. Bake at 350° for 10-11 minutes until the edges are golden brown. Sprinkle with flaky sea salt. Cool for 5 minutes before serving.