• Preheat the oven to 350F, then line a large baking sheet with parchment paper and set aside. In a medium-sized bowl, mix the 1/4 cup granulated sugar and cinnamon together, then set aside.
  1/4 cup granulated sugar, 1/2 tsp cinnamon
• Beat the butter, the brown sugar, and the granulated sugar together until light and creamy.
  2 sticks butter, 1 cup brown sugar, 1/4 cup granulated sugar
• Add in the egg, egg yolk, lemon juice, and vanilla flavoring and mix until combined.
  1 large egg, 1 large egg yolk, 2 tsp vanilla flavoring, 1/4 tsp lemon juice
• Add in the flour, corn starch, baking powder, baking soda, salt, and cinnamon, and mix just until the dry mixture disappears.
  2 & 3/4 cup all purpose flour, 1 tbsp corn starch, 1 tsp baking powder, 1/2 tsp baking soda, 1 & 1/4 tsp cinnamon, 1/4 tsp salt
• Using a large cookie scoop, scoop out 12 equally sized cookie dough balls, roll them between the palms of your hands, then roll them in the cinnamon sugar mixture. Save the leftover cinnamon sugar for later.
• Place the cookies on the prepared baking sheet, leaving 1.5-2 inches between them. Gently flatten the cookies to about 2 cm thick, then bake in the preheated oven for 10 minutes.
  
• Let the cookies cool on the baking sheet for 5 minutes, then transfer to a cooling rack and cool fully.

Make the churro buttercream while the cookies are cooling

• Beat the butter, powdered sugar, brown sugar, cinnamon, vanilla flavoring, and 1-2 tbsp heavy cream together until light and fluffy. If the buttercream is too thick, add 1/2 tbsp heavy cream at a time and mix again until the desired consistency is reached.
  1 stick butter, 1 & 1/2 cup powdered sugar, 1/4 cup brown sugar, 1 tsp cinnamon, 2 tsp vanilla flavoring , 2-3 tbsp heavy cream
• Using a Wilton 35 tip, frost the cooled churro cookies. If you don't have this specific tip, use any tip you have, or just cut the end of a ziplock bag and frost.
• Add 1 tablespoon of brown sugar to the leftover cinnamon sugar that you used to roll your cookie dough in and sprinkle some of it on top of each frosted churro cookie and enjoy.
  1 tbsp brown sugar