Put the sweet potato chunks into a large stockpot, pour in enough water to cover, and set over high heat until boiling. Cook until easily pierced with a fork, then drain thoroughly and move to a large bowl.

Heat the oven to 350°F (175°C). Coat a 2.5 to 3-quart baking dish or a 9x13-inch pan with nonstick spray and reserve.

In the bowl holding the sweet potatoes, mix in the eggs, softened butter, milk, brown sugar, granulated sugar, vanilla, salt, and the optional nutmeg and cinnamon. Using a handheld electric mixer on medium-high, beat until well blended and airy.

Spoon the mixture into the prepared dish and gently level the surface with a spatula; set aside.

In a large microwave-safe bowl, heat the 5 tablespoons of butter on high for about 1 minute until melted.

Stir the brown sugar, flour, and salt into the melted butter, mixing with a fork or your fingers until crumbly and moist.

Fold in the pecans until evenly distributed.

Scatter the topping evenly over the filling.

Bake for about 45 minutes (or if making ahead, cover and refrigerate up to 24 hours before baking), until the top is a light golden brown, the edges are set, and the center is mostly firm. Note: when baking straight from the fridge, expect a longer time—the original took 50 minutes. Because baking time can vary with the pan material (glass or ceramic takes longer than metal), your oven, humidity, and ingredient differences, check for doneness starting at 30 minutes.

Serve right away. Store leftovers in an airtight container in the refrigerator for up to 1 week.