Make the salted caramel first. Place the granulated sugar in a heavy bottom saucepan over medium heat. Do NOT stir, just let it sit and slowly start to melt around the edges. Once it starts liquefying, you can swirl the pan gently. Cook until the sugar turns a deep amber color, about 6 to 8 minutes. Watch it like a hawk, it goes from amber to burnt FAST.

The second it hits that amber color, remove from heat and immediately whisk in the cubed room temp butter (it will bubble up violently, that is normal, keep whisking). Once smooth, slowly stream in the room temp heavy cream while whisking constantly. Whisk in the salt. Pour into a heat safe bowl and let it cool to room temperature, it will thicken as it cools.

Preheat oven to 350°F and line a cupcake pan with 12 liners. Have a baking sheet ready for the mini cookies later.

Make the cupcake batter. In a stand mixer, beat the melted butter and granulated sugar on medium speed until combined, about 1 minute. Add the eggs one at a time, beating well after each, then mix in the vanilla extract.

In a separate bowl, whisk together the flour, cream of tartar, cinnamon, baking powder, and salt. In a measuring cup, stir together the buttermilk and sour cream.

Add the dry ingredients and the buttermilk mixture to the wet in alternating additions, starting and ending with the dry. Mix until JUST combined, do not overmix or you will get tough cupcakes.

Scoop the batter into the cupcake liners, filling each about 3/4 full. Bake at 350°F for 18 to 20 minutes, or until a toothpick inserted in the center comes out clean. Let cool in the pan for 5 minutes, then transfer to a wire rack to cool COMPLETELY.

Make the mini snickerdoodle cookies. In a bowl, whisk together the melted butter, granulated sugar, and light brown sugar until combined. Add the egg yolk and vanilla and whisk again. In a separate bowl, whisk the flour, baking powder, cream of tartar, and cornstarch, then fold into the wet ingredients until just combined.

In a small shallow bowl, stir together the 2 tbsp granulated sugar and 1/2 tsp cinnamon for the coating. Scoop 12 small cookies (about 1 tablespoon each) and roll each one in the cinnamon sugar coating until fully coated. Place on a baking sheet and FREEZE for 10 minutes.

Bake the cookies at 350°F for 8 to 10 minutes, until the tops are just set and slightly crackled. You want these slightly more crisp than your usual chewy cookie because they are going to act as a crunch factor on top of the frosting. Cool completely on the pan.

Make the frosting. In a stand mixer, beat the room temp butter and cream cheese together until smooth and fluffy, about 2 to 3 minutes. Add the cinnamon, vanilla, salt, and heavy cream and mix to combine. Slowly add the powdered sugar 1/2 cup at a time, beating until you reach a thick but pipeable consistency.

Assemble. Make sure your cupcakes are COMPLETELY cool and the salted caramel has cooled and thickened. Use an apple corer or small paring knife to poke a hole in the center of each cupcake, going about halfway down. Spoon the salted caramel into each hole, filling generously. Pipe the frosting on top in a generous swirl, then crown each cupcake with a mini snickerdoodle cookie. Drizzle a little extra caramel over the top if you are feeling fancy. Serve immediately or refrigerate until ready to serve.