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1
Preheat oven to 325 degrees and adjust oven rack to middle position. Grease and flour wells of 18 muffin cups or put in paper liners.
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2
Combine flour, baking soda, and salt in a bowl and set aside.
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3
Whisk water, cocoa, chocolate chips, and espresso (if using) in a large bowl until smooth. Add sugar, sour cream, oil, eggs and vanilla and mix until combined. Whisk in flour mixture until incorporated.
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4
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 before filling or frosting
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5
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.
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6
Stir in butter, vanilla, and salt until combined. Let mixture cool until just warm to touch, about 5 minutes, then whisk/stir in marshmallow cream until smooth; refrigerate until set, about 30 minutes. (I let mine sit overnight and then when I was ready to put it into the cupcakes I just stirred it up to loosen it a bit.
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7
Transfer 1/3 cup marshmallow mixture to pastry bag fitted with small plain tip; reserve remaining mixture for filling cupcakes.
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8
ASSEMBLE CUPCAKES
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9
Microwave chocolate and butter in small bowl, stirring occasionally, until smooth, about 30 seconds.
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10
Cool glaze to room temperature, about 10 minutes. Hollow out a cone from top of each cupcake and fill cupcakes with 1 tablespoon filling each.
