Melt the butter in a medium saucepan over medium heat. Add the brown sugar, and cook until bubbly. Remove from the heat and stir in the water.

Pour the brown sugar mixture into the a 9x13-inch baking dish. Tilt the pan to make sure the syrup is spread in an even layer.

Layer the pears over the syrup. Then place the bread over the pears. Sprinkle the pecans evenly over the bread.

In another bowl (I like to use a large liquid measuring cup), whisk together the eggs, milk, and vanilla extract. Pour this mixture over the bread. If desired, use your hands to gently press the bread down into the custard, making sure the bread is saturated.

Cover the pan and refrigerate overnight.

The next morning, remove the casserole from the refrigerator to take the chill off as the oven is preheating.

Preheat the oven to 350ºF. Place the casserole dish on a larger baking sheet to catch any drips.

Bake the casserole, uncovered, until it becomes puffy and the center is cooked through, about 1 hour.

To serve, cut the casserole into squares, then spoon some of the syrup from the bottom of the pan over each piece.