Preheat oven to 350F.
Grease an 8" springform pan with cooking spray. Set aside.
Line a baking sheet with parchment paper. Set aside.
In a large mixing bowl, combine sugar cookie dough with 3 tbsp cinnamon sugar.
Press half the dough evenly onto the bottom of the springform pan.
Roll remaining dough into tablespoon sized balls. Flatten on baking sheet separated 2". Bake for 10 minutes or until lightly browned. Cool completely on wire rack. Save in an airtight container until ready to garnish.
While cookies are baking, in a stand mixer with paddle or whisk attachment, beat cream cheese until smooth.
Add sour cream and sugar. Beat until light and fluffy.
Add eggs one at a time. Beat well between each addition.
Turn the mixer to low to gently stir in vanilla, 1/2 tsp cinnamon and salt.
Pour mixture over cookie dough in springform pan.
Bake 1 hour. Cake should be slightly jiggly still.
Turn off oven and open door slightly. Let cake cool for 1 hour in oven.
Place in refrigerator for 4-5 hours (or overnight).
When ready to garnish, mix remaining 1/5 tsp cinnamon into the vanilla icing. Transfer to piping bag.
Sprinkle the entire top or the cake with remaining 3 tbsp of cinnamon sugar.
Remove cake from springform pan surround and dollop with icing.
Cut prepared cookies in half and place between dollops.