Instructions

for the sweet potatoes

Adjust oven rack to middle position and heat oven to 350 degrees. Arrange potatoes on aluminum foil–lined baking sheet and bake until tip of knife slips easily into potatoes and any released sugars begin to caramelize on sheet, 1 to 1¼ hours. Let cool until just warm, about 1 hour. (Baked, unpeeled potatoes can be refrigerated for up to 3 days.)

for the crust

Make foil sling for 13 by 9-inch baking pan by folding 2 long sheets of aluminum foil; first sheet should be 13 inches wide and second sheet should be 9 inches wide. Lay sheets of foil in pan perpendicular to each other, with extra foil hanging over edges of pan. Push foil into corners and up sides of pan, smoothing foil flush to pan. Spray with vegetable oil spray.
Process cracker pieces in food processor until finely ground, 
15 to 30 seconds; reserve 1 cup (4 ounces) cracker crumbs for crumble topping. Add sugar, ginger, and nutmeg to remaining crumbs in processor and pulse to combine, about 3 pulses. Add melted butter and pulse until evenly combined, about 8 pulses. Transfer crumb mixture to prepared pan. Using bottom of dry measuring cup, press crumb mixture into even layer in bottom of pan. Bake until crust is slightly puffed and fragrant, 12 to 15 minutes. Transfer pan to wire rack; set aside.

for the crumble topping

Combine sugar, flour, oats, orange zest, lemon zest, ginger, nutmeg, salt, and reserved 1 cup cracker crumbs in medium bowl. Add melted butter and stir until no dry spots remain; set aside.

for the filling

Scoop flesh from cooled potatoes into clean bowl of food processor; discard skins. Process until smooth, about 1 minute, scraping down sides of bowl as needed. Add eggs, sugar, cream, orange juice, lemon juice, ginger, orange extract, vanilla, and salt and process until smooth, 30 to 60 seconds. 
Pour filling into crust (crust needn’t be fully cooled). Using silicone or offset spatula, spread filling to edges of pan and smooth top. Using your hands, squeeze topping mixture into large clumps, then crumble into rough pea-size pieces over filling in even layer (some topping will be more clumped and some more crumbly). Bake until top is golden and edges of filling puff slightly, 40 to 45 minutes. 
Transfer pan to wire rack and let cool completely, at least 3 hours. Using foil overhang, lift bars out of pan. Using sharp chef’s knife, cut into 24 pieces. Serve. (Bars can be stored in an airtight container at room temperature for up to 
3 days.)