Heat oven to 375° F. Line 2 baking sheets with parchment paper or aluminum foil.
With an electric mixer on medium-high, beat the butter, brown and granulated sugars, corn syrup, and vanilla for 3 minutes. Add the egg and beat until combined. In a separate bowl, whisk together the flour, salt, and baking soda. Reduce mixer speed to low and slowly add the flour mixture to the egg mixture.
Add ingredients from the variation of your choice. Unless the directions for the variation state otherwise, form the dough into tablespoon-size mounds. Place on the prepared baking sheets, 2 inches apart.
Bake until lightly browned at the edges, 12 to 15 minutes. Cool on the baking sheets for 5 minutes. Transfer the cookies to wire racks. Cool completely.