1Heat oven to 350°F. Place paper baking cup in each of 24 regular-size muffin cups.
2In large bowl, beat cake mix, eggs, oil and beer with electric mixer on low speed 30 seconds, then on medium speed 2 minutes, scraping bowl occasionally. Divide batter evenly among muffin cups.
3Bake about 20 minutes or until toothpick inserted in center comes out clean. Cool 10 minutes; remove cupcakes from pans to cooling racks. Cool completely, about 30 minutes.
4In medium bowl, beat butter and powdered sugar with electric mixer on medium-low speed until combined. Gradually beat in milk. Cut vanilla bean in half and scrape out seeds. Discard bean; add seeds to frosting. Beat on medium speed until fluffy. Pipe or spread frosting on cupcakes.