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1
Preheat oven to 350 F. Grease a 12-count muffin tin or line it with muffin liners. Place an Oreo cookie in the bottom of each liner.
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2
In a large bowl, sift flour, baking powder, baking soda and salt. Mix well.
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3
In the bowl of an electric mixer fitted with the paddle attachment, mix eggs and sugar until well combined. Gradually add oil and vanilla, mix until just blended.
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4
With the mixer on low, slowly add half the flour mixture; mix until just blended. Add the buttermilk, mix until just blended. Slowly add the remaining flour mixture, scraping down sides of the bowl with a spatula, as necessary, until just blended.
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5
Divide batter evenly among prepared muffin cups. Transfer muffin tin to oven and bake for 18 to 20 minutes. Transfer muffin tin to a wire rack and let cupcakes cool completely.
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6
To prepare the frosting, in a large heatproof bowl, combine sugar and egg whites. Using a handheld electric mixer, beat on high speed until foamy, for a minute or so. Set bowl over a pan of barely simmering water. Beat on high speed until frosting forms stiff peaks, about 10 minutes.
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7
Remove from heat, stir in vanilla and water, and beat for another 2 minutes until frosting thickens. Transfer frosting to a large pastry bag fitted with a wide plain pastry tip and pipe-frost the cupcakes. The frosting will harden slightly as it cools.
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8
Place an Oreo cookie on top of the frosting. Sprinkle a teaspoon of cookie crumbs before serving.
