Line a muffin tin with paper cups. Preheat oven to 375 degrees. With a mixer, cream peanut butter, butter and vanilla in a large bowl until smooth. Gradually add sugar, beating until mix is light and fluffy, about 3 minutes. Add eggs one at a time, beating until all mixed in. Set aside.
In a separate bowl, sift the flour, baking powder, and salt together. Beat a third of the flour mixture into the peanut butter mixture. Do the same with a third of the milk. Repeat this process until everything is well-blended. Scrape down the sides of the bowl btween additions.
For medium cupcakes, fill paper cups two-thirds full. For larger cupcakes, fill to just below top rim. Bake for 20 minutes or until toothpick inserted in the center of cupcake comes out clean. Let cool 10 minutes.
To make the icing:Place chocolate in a medium bowl and set aside.In a heavy 1-quart saucepan,using a wooden spoon, combine cream,corn syrup and butter.Cook over medium heat until hot but not boiling)little beads of water will form on side of pot). Pour cream over chocolate and stir until blended. Voila-ganache!! Let cool completely.
One by one, dip the top of each cooled cupcake into the ganache. Let the excess ganache drip off into the bowl before flipping the cupcake into an upright position. Serve with a big glass of milk !!