Preheat oven to 350°. Spray a 6-well mini loaf pan with baking spray with flour.
In a large bowl, whisk together flour, cocoa, baking powder, and salt. In another large bowl, whisk together milk, brown sugar, melted butter, eggs, granulated sugar, and vanilla. Add milk mixture to flour mixture, whisking until well combined. Divide batter among prepared wells.
Bake until a wooden pick inserted in center comes out clean, 18 to 20 minutes. Remove from oven; immediately sprinkle with marshmallows and pecans. Let cool in pan for 20 minutes. Run a knife around edge of cakes, and remove from pans using an offset spatula. Let cool completely on a wire rack.
In a small saucepan, heat chocolate melting wafers and cream over medium-low heat, stirring frequently, until smooth. Drizzle over cooled cakes.
Recipe by Taste of the South at https://tasteofthesouthmagazine.com/mississippi-mud-mini-loaves/