1. Preheat the oven to 350°F and line two baking sheets with parchment paper.

2. In a large mixing bowl, beat the softened butter, granulated sugar, and brown sugar until light and fluffy.

3. Add the eggs one at a time, then mix in the vanilla extract until fully combined.

4. In a separate bowl, whisk together the flour, baking soda, and salt.

5. Gradually add the dry ingredients to the wet ingredients and mix just until a soft dough forms.

6. Fold in the Lucky Charms cereal and white chocolate chips gently so the cereal stays mostly intact.

7. Scoop the dough into even portions and place them on the prepared baking sheets.

8. Chill the dough balls for 20 to 30 minutes for thicker cookies.

9. Press a few extra cereal pieces and marshmallows onto the tops if you want a more colorful finish.

10. Bake for 10 to 12 minutes, until the edges are lightly golden and the centers still look slightly soft.

11. Let the cookies cool on the baking sheet for 5 minutes, then transfer them to a wire rack to cool completely.