Preheat oven to 350°
In a bowl mix together flour, baking powder, salt, sugar and spices.
In a microwave safe bowl, melt the butter in the microwave, then stir in the pumpkin, evaporated milk and vanilla until til well blended together.
Stir the pumpkin mixture into the flour mixture. When well blended together, fold in the white chocolate chips. Set aside for a minute while you make the topping mixture.
In a small bowl, mix together for the topping the sugar, brown sugar and pecans.
Lightly spray a 9"X 9" or 11"X 7" Deep Dish baking dish with non-stick spray (a 9x13 baking dish is a tad too big).
Spread the pumpkin mixture evenly in the baking dish, then sprinkle the sugar and pecan mixture evenly over the pumpkin mixture.
Pour the very hot water over the top of the dry sugar mixture, and do not stir or mix it in. The pecans will probably float to the top - not to worry.
Bake at 350° for 45 min. The top should be set and not jiggly in the middle.
Let it cool for 5 - 10 min, then serve warm with a big dollop of whipped cream or a scoop of vanilla ice cream.