The Worlds of Katherine Kurtz

I originally posted this in the Thanksgiving thread per Revanne's request, but I decided I'd stick it here too in order to make it easier to find if someone decides to search.  :)

Sweet Potato Casserole
(courtesy of Cooks Illustrated)

7 lbs (approximately 3.2 kg) sweet potatoes (6-8, of equal size)

Streusel Topping:
5 tbsp (74 mL) unsalted butter, cut into 5 pieces and softened
½ cup (118 mL) all purpose flour
½ cup (118 mL) packed dark brown sugar
¼ tsp (1.2 mL) salt
1 cup (237 mL) pecans

Filling:
5 tbsp (74 mL) unsalted butter, melted
2 tsp (10 mL) salt
½ tsp (2.5 mL) ground nutmeg
½ tsp (2.5 mL) pepper
1 tbsp (15 mL) vanilla extract
4 tsp (20 mL) fresh lemon juice
granulated sugar
4 large egg yolks
1½ cups (355 mL) half-and-half

Adjust oven rack to the lower-middle position and heat oven to 400F/200C.  Poke the sweet potatoes and space evenly on a rimmed baking sheet lined with aluminum foil.  Bake the potatoes, turning them once, until they are very tender and can be squeezed easily with tongs, 1 to 1½ hours.  Remove from oven and cut in half lengthwise to let steam escape; cool at least 10 minutes.  Reduce oven temperature to 375F/190C.
While the potatoes are baking, butter a 13x9 (this is in inches, 33 cm x 23 cm, approximate metric size) baking dish. Pulse the flour, brown sugar, and salt in a food processor until blended, about four one-second pulses.  Sprinkle the butter pieces over the flour mixture and pulse until a crumbly mass forms, 6-8 one-second pulses.  Transfer the streusel to a medium bowl.

Once the potatoes have cooled slightly, use a spoon to scoop the flesh into a large bowl.  Transfer about half the potato flesh to food processor.  Using a rubber spatula, break the remaining potato flesh into coarse 1-inch chunks.
Add the melted butter, salt, nutmeg, pepper, vanilla, and lemon juice to the potatoes in the food processor and process until smooth, about 20 seconds. Taste for sweetness, then add up to 4 tbsp (60 mL) granulated sugar, if necessary.  Add the egg yolks.  With the processor running, add the half-and-half through the feed tube and process until blended, about 20 seconds.  Transfer to the bowl with the potato pieces and stir gently until combined.
Pour the filling into the prepared baking dish and spread into an even layer with spatula.  Sprinkle with the streusel, breaking up any large pieces with your fingers.  Bake until the topping is well browned and the filling is slightly puffy around the edges, 40-45 minutes.  Cool at least 10 minutes before serving.