1. Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
2. In a large mixing bowl, cream together butter and sugars until light and fluffy.
3. Add eggs and vanilla extract, mixing until fully incorporated.
4. In a separate bowl, whisk together flour, baking soda, and salt.
5. Gradually mix dry ingredients into the wet ingredients until just combined.
6. Fold in chocolate chips, M&Ms, crushed pretzels, potato chips, and marshmallows.
7. Add any optional mix-ins like white chocolate chips, nuts, or crushed candy canes.
8. Scoop dough into tablespoon-sized balls and place them on the prepared baking sheet.
9. Lightly press the dough balls to flatten slightly.
10. Sprinkle a small amount of sea salt on top for extra flavor.
11. Bake for 9-12 minutes or until the edges are lightly golden.
12. Remove from the oven and let cookies cool on the baking sheet for a few minutes.
13. Transfer cookies to a wire rack to cool completely.
14. Store in an airtight container at room temperature for up to 3 days.
15. Freeze any extras for longer storage if needed.
16. Enjoy your delicious Kitchen Sink Christmas Cookies!