Step 1

Grease a 9x13-inch baking dish.

Step 2

Using a doughnut cutter, cut 12 circles and 12 holes from the bread slices. Set both aside.

Step 3

Tear the remaining bread into pieces and place the pieces in the prepared baking dish.

Step 4

Layer in the cheese, the asparagus, and the ham.

Step 5

Arrange the bread circles and the bread holes on top of the ham layer.

Step 6

Lightly beat the eggs with the milk.

Step 7

Add the onion, the salt, and the mustard to the egg mixture and mix well.

Step 8

Pour the egg mixture over the bread circles and bread holes.

Step 9

Cover the bake and refrigerate it for at least 6 hours and up to overnight.

Step 10

Preheat the oven to 325 degrees F.

Step 11

Bake the casserole uncovered until the top is a light golden-brown, about 55 minutes.

Step 12

Let the bake stand for 10 minutes.

Step 13

Serve.