How to Make It
For each cake, combine all-purpose flour, granulated sugar, kosher salt, unsweetened cocoa, chopped toasted pecans, bittersweet chocolate chips, baking powder, and cinnamon in a small food-safe gift bag. Place mini marshmallows in a separate bag. Place both bags inside a 12-oz. microwavable mug.
To prepare each cake, stir whole milk, canola oil, and vanilla extract into the dry ingredients in mug. Microwave on HIGH until cake rises and is cooked through, 60 to 90 seconds. Remove from microwave; sprinkle marshmallows on top. Microwave on HIGH 5 more seconds. Serve immediately.