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1
Preheat the oven to 350.
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2
Line a 12-cup muffin tin with paper or foil liners.
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3
In a medium saucepan, melt the butter with the vegetable oil and water over low heat.
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4
In a large bowl, sift the flour with the sugar, cocoa powder, baking soda and salt.
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5
Add the melted butter mixture and beat with a handheld mixer at low speed until smooth.
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6
Add the egg and beat until incorporated, then add the buttermilk and vanilla and beat until smooth, scraping the bottom and side of the bowl.
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7
Pour the batter into the lined muffin tins, filling them about three-fourths full.
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8
Bake the cupcakes in the center of the oven for about 25 minutes, until springy and a toothpick inserted in the center comes out clean.
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9
Let the cupcakes cool slightly, then transfer them to a rack to cool completely.
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10
In a medium bowl, using a handheld electric mixer, beat the softened butter at medium speed until smooth.
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11
Add the confectioners' sugar, vanilla extract and salt and beat the mixture at low speed just until combined.
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12
Increase the mixer speed to medium and beat until smooth.
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13
Add the milk or heavy cream and beat until light and fluffy, about 2 minutes.
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14
Spread the frosting on the cooled cupcakes, top with the crushed Oreos and serve.
