Dulce de leche filling:

1. Line a small pan or plate with parchment paper
2. Divide the dulce de leche into 5 30g portions (about 1 heaping tablespoon each). I recommend using a round tablespoon measure so each portion is round in shape (spray the spoon with a little oil so the dulce de leche doesn't stick). Place the balls on the parchment paper, not touching, and put in the freezer for ~20 minutes while you work on the cookie dough

Churro cookie dough:

1. Whisk the butter, granulated sugar and light brown sugar in a large bowl at medium high speed for 2-3 minutes until the mixture is fluffy and light in color, scraping the bowl along the way
2. Add the egg, egg yolk and vanilla, and whisk for another minute to combine
3. Sift the flour, baking powder, baking soda, salt and cinnamon in a separate bowl and mix to combine
4. Add the dry ingredients to the cookie dough in 2 batches, and fold gently with a rubber spatula until just mixed and no streaks of flour can be seen. If the dough feels firm too soft or sticky (which can happen if the butter was too soft), place the bowl in the fridge for 10-15 minutes until the dough is easier to work with

Cinnamon sugar coating:

1. Mix the cinnamon and sugar for the coating in a bowl

Assembly:

1. Divide the cookie dough into 5 5oz portions (this should use up almost all of the dough with a little leftover, which you can bake as a small, bonus cookie)
2. Remove the dulce de leche scoops from the freezer
3. Working one cookie dough ball at a time, gently flatten into a disc in your palm, place a dulce de leche scoop in the middle, and seal the cookie dough around it so the dulce de leche is completely covered in cookie dough. Gently shape the dough into a round ball which will weigh ~6oz
4. If you want the cookies to be thick and gooey, leave the balls round. If you want the cookies to be flatter, gently press the balls into discs (2.5 to 3" wide)
5. Generously coat each cookie ball with cinnamon sugar on all sides, and place on a sheet / plate. Save the leftover cinnamon sugar
6. Refrigerate the dough for at least 6 hours, and ideally overnight for the best results

Baking:

1. Once the cookie dough has chilled, pre-heat your oven to 375F (conventional / no fan) and line a large, light colored cookie sheet with parchment paper.
2. Remove the cookie dough balls from the fridge, and coat them in cinnamon sugar again
3. Place the cookie dough balls on the baking sheet, keeping at least 3" between them
4. Bake at 375F for 5 minutes, then drop the temperature to 340F and bake for another 12-14 minutes (total baking time of 17-19 minutes). When perfectly baked, the cookies should be golden in color, set around the edges, and soft to touch in the middle
5. Remove from the oven and let the cookies rest for at least 20 minutes until they feel set

Dulce de leche cream cheese frosting:

1. Add the cream cheese and dulce de leche to a bowl, and whisk on medium speed for 1-2 minutes until combined and creamy. Scrape the bowl 1-2 times
2. Add the chilled heavy cream and salt, and whisk for another 1-2 minutes until the mixture reaches medium peaks and holds shape. Do not overmix
3. Transfer to a piping bag fit with a French star piping tip
4. Once the cookies have cooled down, pipe the cream cheese frosting on top in swirls, starting from the middle and going outwards with steady pressure
5. Finish with a sprinkle of cinnamon sugar
6. Serve & enjoy!