Place the cubed rolls in a large bowl. Drizzle the hot milk over the bread, stir and let sit for 1/2 hour. If it is still dry, add more milk. If you have milk at the bottom of your bowl, pour it out. Add the egg and 1/2 cup flour. Here is the fun part, mix it all together by hand to incorporate and portion 5 dumplings from the batter. With wet hands, press the batter together, shape and roll into a ball.
Try a test dumping by boiling 2 gallons of water in a large stockpot and add 1 Tablespoon salt. Place a dumpling into the boiling salted water, and let return to a boil. Cover the pot and cook the dumpling for 15 minutes. Remove with a slotted spoon. If it falls apart, add more bread, and try a second test dumpling.
To test if done, cut open with a serrated knife, the dumpling should be cooked all the way through, if it is doughy, the remaining dumplings in the pot will need 3-5 minutes more.
I used the Torta rolls from Costco, several days old is best.