The first time I made these I found that for so many muffins there was not enough streusel topping for my liking, so I doubled the topping mixture the second time --- follow the directions for the muffins, add in the whites *after* the flour and mix for no more than 1 minute --- although I haven't tried it as yet, I imagine this would work using firm ripe finely chopped strawberries in place of blueberries, these are *very* good!