Mix 1 tablespoon of butter with brown sugar and gochujang until it forms a paste.
Mix the oil and milk with the remaining sugars and vanilla.
Add the flour, baking soda, salt, and cinnamon. Mix until dough is cohesive. Refrigerate the dough for 10-15 minutes.
While the dough chills, preheat your oven to 180 degrees C. Line two baking sheets with parchment paper or silicone mats.
Remove the dough from the fridge. Add dollops of the gochujang caramel paste to the cookie dough. Use a stiff spatula to gently swirl the caramel into a marbling pattern in the dough, ensuring you maintain a visible color contrast.
Use a large cookie scoop (about 3 tablespoons) to form 12 cookies, placing 6 on each baking sheet with enough space between them. If using a smaller scoop, you can make 24 cookies.
Bake the cookies for 11-13 minutes, until they show cracks on the top and are golden around the edges. Rotate the pans halfway through for even baking.
Allow the cookies to cool on the baking sheets for about 3 minutes before transferring them to a cooling rack.
Store the cookies in an airtight container at room temperature. They'll stay good for up to three days.
