Preheat the oven to 375°F (190°C). Line two baking sheets with parchment paper.
In a medium bowl, whisk together the all-purpose flour, baking soda, and salt. Set aside.
In a large bowl, using an electric mixer, beat the softened unsalted butter, granulated sugar, and light brown sugar until creamy and smooth, about 2 minutes.
Add the vanilla extract and eggs to the butter mixture, one at a time, beating well after each addition until fully incorporated.
Gradually add the flour mixture to the wet ingredients, mixing on low speed until just combined.
Fold in the semisweet chocolate chips and mini marshmallows gently with a spatula, ensuring they are evenly distributed.
Using a tablespoon or cookie scoop, drop rounded spoonfuls of dough about 2 inches apart onto the prepared baking sheets.
Bake in the preheated oven for 10 to 12 minutes or until the edges are golden brown but the centers remain soft.
Remove the cookies from the oven and let them cool on the baking sheets for 5 minutes before transferring to wire racks to cool completely.