Old Fashioned Chocolate Layer Cake is a tall and stately two layer chocolate cake adapted from Cook's Illustrated. For best results, use Dutch-process cocoa and real buttermilk.
I usually make cakes with a handheld mixer. Since my handheld mixer doesn't have a true "low" speed, I mix the flour and buttermilk mixture in by hand (meaning with a heavy duty scraper or mixing soon) to avoid over-beating. If using a stand mixer with a paddle on low speed, you don't run much of a risk of over-beating, so in that case it's fine to just use the paddle.