Preheat the oven to 350°F (175°C) and prepare a baking sheet with parchment paper.

In a medium bowl, whisk together the flour, cocoa powder, baking soda, and salt. Set aside.

In a large bowl, whisk together melted vegan butter, light brown sugar, applesauce, and vanilla until smooth and creamy.

Stir the dry ingredients into the wet mixture until just combined. Fold in chopped vegan dark chocolate.

Cover the bowl with the dough and refrigerate for 15 minutes.

Use about 2 tablespoons of dough per cookie, rolling into balls, and place them on the prepared baking sheet with 2 inches of space between.

Bake for about 10 minutes until the edges are set but the centers remain soft.

After baking, gently press a marshmallow half into the center of each cookie and return to the oven for an additional 2–4 minutes until slightly puffed.

Let the cookies cool on the baking sheet for about 10 minutes and then transfer to a wire rack to cool completely.

Melt finely chopped semi-sweet chocolate in a double boiler or microwave in 20-second intervals, stirring until smooth.

Spoon melted chocolate over each marshmallow-topped cookie. Add sprinkles if desired, and allow to set at room temperature for 30–60 minutes before serving.