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1
Make the cake: 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 bowl, whisk the flour with the cornstarch, baking powder and salt.
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4
In a large bowl, using a handheld electric mixer, beat the sugar with the eggs and vanilla extract at medium-high speed until smooth and thickened slightly, about 3 minutes.
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5
Add the butter and oil and beat until incorporated, scraping the bottom and side of the bowl.
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6
Add the dry ingredients and milk in 3 alternating batches, beating well between additions.
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7
Carefully pour the batter into the lined muffin tins, filling them about two-thirds full.
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8
Bake the cupcakes in the center of the oven for 20 to 23 minutes, until springy and a toothpick or cake tester inserted in the center comes out clean.
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9
Let the cupcakes cool slightly in the muffin tin, then transfer them to a wire rack to cool completely.
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10
Meanwhile, make the frosting: In a small saucepan, combine the granulated sugar with the water and bring to a boil over moderately high heat, stirring constantly until the sugar has dissolved, 2 to 3 minutes.
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11
In a large bowl of a standing electric mixer, beat the egg whites with the pinches of cream of tartar and salt until soft peaks form.
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12
With the mixer at medium speed, carefully pour the hot sugar syrup into the egg whites.
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13
Continue beating the frosting until cool and billowy, about 5 minutes.
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14
Mix the frosting with the chocolate covered peanuts and peanut butter to taste, spread on cooled cupcakes and serve.
