Melt the butter in a large skillet over medium-high heat. Add bread cubes and toss until golden brown, about 5-10 minutes. Transfer to a large bowl and set aside.
Add bacon and onions to the skillet and sauté until browned. Add the mixture to the bread.
In a small mixing bowl whisk together the eggs and milk. Pour over bread mixture. Season with salt, pepper, and nutmeg. Add parsley and mix until well combined. Set aside to rest for 10-15 minutes.
Bring a large saucepan of salted water to a boil. Moisten your hands and form bread mixture into 6 balls. Add balls to boiling water and cook until firm, about 15-20 minutes. Remove dumplings with a slotted spoon and drain briefly on paper towels. Transfer to a serving dish and sprinkle with parsley.
Serve dumplings alongside any meat or mushrooms with gravy or a creamy sauce.