Heat oven to 350 degrees F. Line 12-cup muffin pan with cupcake liners; set aside.
In large bowl, sift together flour, sugar, cocoa, baking soda and salt.
Dissolve 1 1/2 teaspoons espresso powder in 1 cup water; add to flour mixture.
Add oil and vinegar to flour mixture; blend on low speed 1 minute, scraping bowl often.
Beat on medium speed 1 minute, until well blended. Divide batter evenly among muffin cups.
Bake at 350 degrees F. for 18-20 minutes, until toothpick inserted comes out clean. Remove from pan and cool completely.
In medium bowl, dissolve 1 1/2 teaspoons espresso powder in 1 tablespoon water.
Add butter, vanilla and powdered sugar; blend on low speed 1-2 minutes, until combined.
Beat on medium speed 2 minutes, adding additional water 1 teaspoon at a time, until frosting is smooth and creamy. Pipe or spread onto cooled cupcakes.