Scoop the batter into 8 muffin cups, using a spoon or an ice cream scoop. The batter should be slightly mounded above the edge. Sprinkle the streusel topping evenly over the mounds of batter and press it into the batter slightly.
Bake for 32 to 35 minutes, rotating the pans halfway through. The muffins are ready to come out when they smell nutty and their bottoms are a dark golden-brown. Remove the pans from the oven, twist each muffin out, and place it on its side in the cup to cool. This ensures that the muffin stays crusty instead of getting soggy. I think I'll use a cooling rack next time instead.
Also, the book says that these muffins are best when warm from the oven or later that day. Although they did taste the best that first day, they still tasted good 2-3 days later. They can also be frozen and reheated.