Cook sweet potato in a medium saucepan in boiling water to cover 10 minutes or until tender. Drain. Beat sweet potato at high speed of an electric mixer until smooth. Add milk, 1 tablespoon brown sugar, orange juice, salt, allspice, and egg yolk; beat at high speed until smooth.
Beat egg white at high speed of an electric mixer until stiff peaks form; fold egg white into sweet potato mixture. Spoon mixture into 2 (6-ounce) ramekins coated with cooking spray. Sprinkle remaining 1 tablespoon brown sugar and pecans evenly over potato mixture. Bake at 400° for 20 to 25 minutes or until thoroughly heated.