Slice and cut the bread into 1-inch cubes. Let the cubed bread sit out uncovered for a few hours or up to 1 day. (If you don’t have enough time, see Bread note below.)

Grease a 9×13-inch baking dish (or any 3.5-4 quart baking dish) or spray with nonstick spray. Spread cubes of bread in the dish.

Whisk pumpkin, brown sugar, pumpkin pie spice, eggs, milk, and vanilla extract together in a large bowl. Pour evenly over bread.

Cover the pan tightly and place in the refrigerator for at least 3 hours and up to 1 day. This gives the bread a chance to soak up the pumpkin custard and is a key step in this recipe.

Mix the brown sugar, flour, and cinnamon together. Add the cold butter and using a pastry cutter or fork, cut butter into the brown sugar mixture until pea-size crumbles form. You can also use your hands to mix it together. Stir in the pecans. Cover and refrigerate (separately, do not add to soaking casserole) until ready to use in step 7. Can be refrigerated for just 15 minutes or up to 1 day. The colder it is, the less likely it will sink down and get lost in the casserole.

Remove casserole from the refrigerator and preheat oven to 350°F (177°C).

Sprinkle crumb topping evenly over casserole and bake uncovered for 20 minutes, and then cover with aluminum foil and bake for an additional 25-35 minutes or until center appears set and is no longer runny. The total time this casserole takes is 45-55 minutes.

Remove from the oven and cool for 5 minutes before serving. Casserole deflates slightly as it cools. Feel free to drizzle maple syrup on top of entire casserole or on individual servings.

Cover leftovers tightly and store in the refrigerator for 2-3 days.