Add bacon to the hot skillet and cook until crispy, about 7 to 10 minutes. Remove to a paper towel lined plate to drain.
In a large mixing bowl, beat together the eggs and milk.
Slice the bread into 1/2-inch cubes and place in the mixing bowl.
Core the apples and cut into bite-sized pieces. Add to the mixing bowl along with almost all of the bacon and raisins, if desired.
Use a wooden spoon to mix everything together, making sure all of the bread is coated in the egg mixture.
Pour into a 9-inch by 13-inch casserole dish or lasagna pan (with high sides) and spread into an even layer. Sprinkle to remaining bacon on top.
Preheat your oven to 350 degrees F. Do this after you combine everything so the casserole ingredients can marry a bit before baking.
Bake for 40 minutes or until the casserole is set and golden on top.
Carefully remove from the oven and let stand for 5 minutes before serving.
Notes
Since there are lots of raisins in the bread, it's your choice to add extra raisins into the casserole.If you prefer the casserole on the sweeter side, mix together 1/4 cup sugar and 1 teaspoon cinnamon. Then sprinkle it all over the top of the casserole. It'll create a sweet & crunchy crust.