Can I make these gluten-free?

Yes—substitute Bob’s Red Mill 1-to-1 Gluten Free Flour . The texture will differ slightly, but they stay delicious.

Can I replace the butter with margarine or vegan butter?

You can, but butter gives the best flavor and texture. If you go vegan, use a solid vegan butter substitute and an egg replacer.

Not entirely. They soften and collapse into little pockets of goo that taste like mini sips of hot chocolate. Yum.

Keep an eye on them. Bake until edges set but centers stay soft. If you see browning, pull them out sooner.

Yes, but chill the dough first and add a touch more flour if needed for rollability.

Scale

1 cup (225 g) unsalted butter, softened
1 cup (200 g) packed brown sugar
½ cup (100 g) granulated sugar
2 large eggs
2 teaspoons vanilla extract
2 cups (250 g) all-purpose flour (King Arthur recommended; for gluten-free use Bob’s Red Mill 1-to-1)
¾ cup (75 g) unsweetened cocoa powder
1 teaspoon baking soda
½ teaspoon salt
1 cup (170 g) chocolate chips or chopped chocolate
1 cup mini marshmallows

Heat the oven to 350°F (175°C). Line a baking tray with parchment paper.
In a roomy mixing bowl, beat the softened butter with the brown and granulated sugars until the mixture becomes pale and fluffy.
Beat in the eggs one at a time, then stir in the vanilla until the batter is smooth.
In another bowl, combine the flour, cocoa powder, baking soda, and salt—whisk to blend evenly.
Add the dry ingredients to the wet mixture in batches, stirring until everything is just incorporated. Avoid overworking the dough.
Fold in the chocolate pieces and the mini marshmallows gently so they’re distributed throughout the dough.
Drop rounded tablespoons of dough onto the prepared sheet, spacing them apart to allow for spreading.
Bake for about 9–11 minutes. The cookies are ready when the edges look set but the centers are still slightly soft.
Let the cookies rest on the baking tray for a few minutes to finish setting, then move them to a wire rack to cool completely.