These buttery pecan biscuits won't last long after they come out of the oven.
Heat oven to 400 degrees. Place the pecans on a baking sheet. Toast in oven until golden and fragrant, 8 to 10 minutes. Let pecans cool.
In the bowl of an electric mixer fitted with the paddle attachment, cream butter and sugar on medium speed until light and fluffy, 2 to 4 minutes. Add egg and vanilla; incorporate.
In a medium bowl, whisk together flour, cornmeal, baking powder, and salt. On low speed, add flour mixture to butter mixture. Mix until combined, about 30 seconds.
Transfer dough to a clean work surface, and divide into four equal portions. Place one portion between two 12-inch-square pieces of parchment. Roll out dough to a 3 1/2-by-9-inch rectangle. Repeat with the remaining 3 portions dough. Transfer to baking sheets; chill at least 10 minutes.
In the bowl of food processor, process pecans, cinnamon, and brown sugar until nuts have been finely chopped, 12 to 15 seconds. Transfer mixture to a medium bowl.
Remove top pieces of parchment from dough. Brush one lightly with egg white; sprinkle 1/4 cup pecan mixture over top. Brush second rectangle lightly with egg wash. Invert second rectangle over first; remove parchment on top. Repeat layering process, leaving top rectangle uncoated. Trim to a 3 1/4-by-8 1/2-inch brick. Wrap; chill overnight.
Heat oven to 350 degrees. Line two baking sheets with parchment. Cut the brick into 1/4-inch-thick rectangles; place rectangles on baking sheets, spaced 2 1/2 inches apart.
Bake biscuits until light golden, 12 to 15 minutes. Transfer to a wire rack to cool. Bake or freeze remaining dough. Store in an airtight container up to 2 weeks.