Preheat your toaster oven to 375°F and lightly grease your cookie sheet or line with a silpat.
In a medium bowl beat together the butter and brown sugar using a hand-mixer until light and fluffy (1 to 2 mins). Beat in the pumpkin, vanilla and egg yolk. Set mixer to a low speed and add flour, baking soda, pumpkin pie spice and salt mixing just until combined.
Drop dough by 1 1/2 tablespoon scoops onto prepared cookie sheet at least 1-inch apart (cookies will spread while baking).
Bake for 8 to 11 minutes until the cookies are set with lightly browned edges. Cool cookies for 3 minutes on sheet before transferring to a rack to cool completely.
While cookies cool place white chocolate chips in a microwave safe bowl. Microwave chips on high for 30 seconds, stirring every 10 seconds until smooth. Drizzle melted chocolate over cooled cookies and enjoy.
Convection Toaster Ovens: Bake at 350℉ for 7 to 9 minutes
Cook time includes 20 minutes of inactive cooling time.