Wash hands with soap and water.
Lightly grease a 3-quart casserole dish.
Gently rinse shallots under cold running water.
In a large skillet over medium-high heat, warm oil. Add minced shallots to skillet and sauté 1 minute. Add chicken strips and cook 5 minutes more. Do not rinse raw poultry or meat.
Wash hands with soap and water.
Place a layer of bread cubes in the bottom of the dish. In alternating layers, place chicken, spinach, sundried tomatoes, cheese and bread, ending with a sprinkling of bread on top.
Add eggs to a large bowl.
Wash hands with soap and water after handling raw eggs.
Add milk, mustard and nutmeg to egg mixture and combine with a whisk.
Pour mixture over the casserole, cover and refrigerate on lowest shelf 4 hours or overnight.
Preheat oven to 350 °F. While oven heats, remove casserole from refrigerator. Place casserole in oven and bake 35-40 minutes, until golden brown on top and internal temperature reaches 165 °F on food thermometer.
Remove from oven and cool 5 minutes before serving.