MAKE BATTER Adjust oven rack to middle position and heat oven to 325 degrees. Grease and flour 12-cup muffin tin. Combine flour, baking soda, and salt in bowl. Whisk water, cocoa, chocolate chips, and espresso in large bowl until smooth. Add sugar, sour cream, oil, eggs, and vanilla and mix until combined. Whisk in flour mixture until incorporated. Divide batter evenly among muffin cups. Bake until toothpick inserted into cupcake comes out with few dry crumbs attached, 18 to 22 minutes. Cool -cupcakes in tin 10 minutes, then turn out onto wire rack and cool completely.
PREPARE FILLING Combine water and gelatin in large bowl and let sit until gelatin softens, about 5 minutes. Microwave until mixture is bubbling around edges and gelatin dissolves, about 30 seconds. Stir in butter, vanilla, and salt until combined. Let mixture cool until just warm to touch, about 5 minutes, then whisk in marshmallow creme until smooth; refrigerate until set, about 30 minutes. Transfer 1/3 cup marshmallow mixture to pastry bag fitted with small plain tip; reserve remaining mixture for filling cupcakes.
ASSEMBLE CUPCAKES Microwave chocolate and butter in small bowl, stirring occasionally, until smooth, about 30 seconds. Cool glaze to room temperature, about 10 minutes. Insert the tip of a paring knife at a 45-degree angle about 1/4 inch from the edge of the cupcake. Cut out and remove the cake cone. Cut off all but the top 1/4 inch of the cone, leaving a circular disc of cake. Discard—better yet, eat!—the bottom of the cone. Using a spoon, fill each cupcake with 1 tablespoon of the marshmallow mixture. Replace tops, frost with 2 teaspoons cooled glaze, and let sit 10 minutes. Using pastry bag, pipe curlicues across glazed cupcakes. Serve. (Cupcakes can be stored in airtight container at room temperature for 2 days.).