Roast the sweet potatoes. Heat the oven to 400°F. Scrub the sweet potatoes, pat dry, and pierce several times with a fork. Place on a lined baking sheet and roast for 60–90 minutes, until completely tender. Let cool until comfortable to handle, then peel.

Brown the butter. While the sweet potatoes roast, place the butter in a light-colored saucepan over medium heat. Stir frequently as it melts and foams. When the milk solids turn golden brown and the butter smells nutty, immediately pour into a heatproof bowl, including the browned bits. Let cool until warm, not hot.

Smooth the sweet potatoes. Beat the peeled sweet potatoes in a large mixing bowl until smooth. Scrape down the bowl and remove any fibrous strands that collect on the beaters.

Mix the filling. Add both sugars and the cooled brown butter. Mix until combined, then add the evaporated milk, vanilla, cinnamon, nutmeg, and either the orange juice or lemon extract. Blend in the flour.

Add the eggs. Make sure the mixture is lukewarm rather than hot. Lightly beat the eggs separately, then mix into the filling on low speed just until incorporated. Scrape down the bowl and stir to combine.

Prepare the crusts. Reduce the oven to 350°F and let it reach that temperature. Partially bake two 9-inch deep-dish pie crusts for 10 minutes. If using packaged crusts, follow the package directions for supporting the crust during partial baking.

Fill and bake. Divide the filling evenly between the prepared crusts, leaving a little space below the rims. Place on a baking sheet and bake on the middle rack at 350°F for about 1 hour. Begin checking after 50 minutes. The edges should be set and the centers should jiggle only slightly. Shield the crust edges with foil if they brown too quickly.

Cool and chill. Let the pies cool on a wire rack, then refrigerate within 2 hours of coming out of the oven. Chill until the filling is fully set before slicing. Keep leftovers refrigerated.