If you're kneading by hand, transfer the dough to a lightly oiled work surface; knead it for 3 minutes; allow it to rest for 15 minutes, then continue kneading till smooth, an additional 8 to 10 minutes. You can also simply knead the dough using the dough cycle of your bread machine.
Towards the end of the rising time, preheat the oven to 350°F.
In a small bowl or mini processor, combine the streusel ingredients, cutting in the butter until the mixture is crumbly. If you're using a mini processor, watch carefully; streusel will go from crumbly to a cohesive mass in just a second or so.
Brush the loaves with some (or all) of the remaining beaten egg, and add the streusel, using your fingers to gently apply it to the dough, being careful not to deflate the loaf.
Bake the bread for about 45 minutes, tenting the loaves lightly with aluminum foil for the final 15 minutes or so if it appears to be browning too quickly.