In a small bowl, combine softened (not melted) unsalted butter, brown sugar and gochujang.

Separately, in a large bowl, add unsalted butter, granulated sugar, salt and vanilla extract (optional). Use a hand mixer to combine until pale and fluffy.

Sift in the flour, baking soda and ground cinnamon (optional), then use a spatula to mix until a dough forms.

Cover the cookie dough bowl with plastic wrap, then refrigerate for 15 minutes.

Add 3-4 blobs of gochujang caramel on top of the cookie dough. Use a spoon or a knife to swirl the gochujang mixture into the cookie dough, without mixing it in. It should create large, distinct ribbons of color.

Use a small ice cream scoop to form cookies, ensuring each cookie has some of the gochujang butter on top. Place the cookies on lined sheets, spaced at least 3 inches apart, as they spread a lot whilst baking.

Optional, mix gochugaru and sugar in a small bowl, then sprinkle a little of the mixture on top of each cookie.

Bake for 10-12 minutes, or until the edges are slightly golden-brown in color. Allow cookies to cool down completely on the baking sheet.