You can make the strawberry sauce in advance and store it in the refrigerator. Before serving, reheat on the stove to 165 degrees. If the sauce is too thick, thin with water, 1 tablespoon at a time.
Coat a 9-inch by 13-inch baking dish with nonstick spray. Spread half the bread cubes in the bottom of the dish. Add the cream cheese in pieces evenly over the bread. Top with 2 cups strawberries and remaining bread.
In a large bowl, beat eggs. Beat in half-and-half, maple syrup, and vanilla until smooth. Pour over the casserole. Cover with foil and chill at least 8 hours or overnight. Remove from the refrigerator at least 30 minutes, or up to 1 hour, before baking.
Adjust an oven rack to the middle position and preheat oven to 350 degrees. Bake covered for 45 minutes. Remove foil and bake until golden brown and set in the middle, about 10 minutes longer.
To make the sauce:
Meanwhile, in a medium saucepan over medium-high heat, whisk together sugar, water, and cornstarch. Bring to a boil, reduce heat to medium, and boil for 3 minutes, stirring constantly.
Stir in strawberries and simmer until the berries soften and break down, about 8 to 10 minutes. Stir in butter until melted, then pour the sauce over the casserole. For best results, let the casserole rest at least 10 minutes before slicing.
Notes
Bread: I use a soft sandwich bread in this recipe. If you use more than 12 slices, you won't have enough liquid to moisten the casserole properly. Dry the bread up to 3 days in advance on the counter (keep it covered with a dry kitchen towel) or cube and dry in a 300-degree oven for 30 minutes.
Strawberries: Either fresh or frozen strawberries work in this recipe. I use frozen berries because they are more convenient and economical.