½ cup (70 grams) mashed sweet potatoes½ cup (113 grams) non-European-style unsalted butter, cubed½ cup (100 grams) granulated sugar½ cup (110 grams) firmly packed light brown sugar1 large egg yolk (19 grams), room temperature1 teaspoon (4 grams) vanilla extract1½ cups (188 grams) all-purpose flour½ teaspoon (3 grams) baking soda½ teaspoon (2 grams) kosher saltPecan Praline Sauce (recipe follows)
In a medium saucepan, cook potatoes over medium heat, stirring frequently, until thickened, slightly darkened in color, fragrant, and some liquid has cooked off, 5 to 6 minutes. Stir in butter until melted. Transfer to a medium heatproof bowl. Let cool slightly.
Whisk sugars into potato mixture until well combined. Whisk in egg yolk and vanilla.
In another medium bowl, whisk together flour, baking soda, and salt. Gradually add flour mixture to potato mixture, folding until fully combined. Cover and refrigerate for at least 40 minutes or up to 2 hours.
Preheat oven to 350°F (180°C). Line baking sheets with parchment paper.
Using a 2-tablespoon spring-loaded scoop, scoop dough, and place 2 inches apart on prepared pans.
Bake until edges are lightly browned, 15 to 20 minutes. Let cool completely on pans.
Top cooled cookies with Pecan Praline Sauce. Best served same day as made. If making ahead, store cookies without sauce in an airtight container for up to 3 days. Top with Pecan Praline Sauce just before serving.