Coffee cakes come in two types--leavened by baking powder and/or soda, or by yeast. The first is what most Americans would call a coffee cake, that tender, cakey variety which is often made with sour cream. The other kind is more recognizable as cinnamon rolls.
This is the sour-cream variety and really couldn't be easier. Inexperienced bakers--that's us--should have no trouble with it. The result has a tender crumb and is nice and buttery -- there is almost as much topping as batter, so it melds in the heat into a caramelized, sweet, crunchy goodness. One could easily double the batter-to-topping ratio to make it a little more cakey.
GG's Coffee Cake
For the batter
For the topping
Sift together the dry batter ingredients (or place in a bowl and fluff together with a fork until well-combined), then add to the sour cream mixture.
Combine the topping ingredients, cutting the butter with the other ingredients until no large chunks of butter remain. Sprinkle the topping over all of the batter, then use a butter knife to haphazardly slice into wet batter, incorporating some of the topping mixture.