Cream butter and sugars until creamy; about 5 minutes.
Mix in egg yolk and extracts.
Whisk together flour, cornstarch, and salt in separate bowl.
Gradually pour dry mixture into wet mixture. Mix on low just until combined.
Shape dough into a disk. Wrap in plastic wrap and chill in refrigerator for 15 minutes or overnight. If refrigerating overnight, allow dough to come to near room temperature before rolling it. Lightly flour flat surface (or parchment paper. I like to use 2 sheet to roll out dough).
Roll dough into 12 X 10-inch rectangle.
In a small bowl, melt butter in microwave. Stir in brown sugar, cinnamon, salt, and corn syrup and mix until combined.
Imminently pour mixture evenly over dough. Using a spatula, move the filling to carefully cover the dough, leaving about ½-inch of space on all sides without any filling.
Turn the longer side (12-inch) of dough to face your hands. Carefully and tightly roll dough into log. I find it useful to carefully pull the parchment paper sheet over the top from underneath. This keeps the dough in shape and ensures a tight roll, allowing the parchment paper to guide it. Wrap in parchment paper and freeze on a sheet pan for 15 minutes.
Preheat oven to 375°F. Line baking sheet with parchment paper.
Cut slices into ¼-inch thick. I cut dough into half, then cut into 15 slices in each half or 30 slices if cutting whole dough at once.
Bake in oven for 10-12 minutes. Allow to cool before frosting.
To make the frosting, cream the cream cheese until smooth. Add butter and cream. Beat in salt, powdered sugar, milk.
Mix in extracts and beat until well combined.
Frost cookies. Top with purple, yellow, and green sprinkles.