Preheat your oven to 350°F (175°C) and line your baking sheets with parchment paper.

In a bowl, whisk together the flour, baking soda, and salt until well combined.

In another mixing bowl, beat the softened butter, brown sugar, and granulated sugar together until light and fluffy (about 3-4 minutes).

Add in the vanilla extract and the egg, mixing well until combined.

Gradually mix in the dry ingredients until just blended.

Gently fold in the Lucky Charms cereal and mini marshmallows, being cautious not to crush them.

Using a tablespoon, drop balls of dough onto the prepared baking sheets, leaving space in between.

Bake for 10-12 minutes, until the edges are golden.

Let them cool for a few minutes on the sheet before transferring to a wire rack to cool completely.