Preheat the oven to 350 with a rack in the middle. Butter (or spray an 8x8 square baking pan and line with parchment or foil for easy removal.

Melt the butter in a saucepan until bubbly, remove from heat and add the oil, cocoa powder, both sugar and vanilla and stir with a wooden spoon or a spatula until combined. Add the eggs one at a time, stirring to fully incorporate.

Add the flour, baking soda and salt to the wet mixture and stir with wooden spoon or spatula just until combined.

Pour the batter into the prepared baking pan. Using a tablespoon-sized spoon, place small spoonfuls of the biscoff cookie butter on top of the brownie batter. You can swirl it around a bit using a dowel or a toothpick or even a butter knife. Please note - it won’t swirl super easily because the cookie butter is not soft. If you like swirls, you can microwave the cookie butter for a few seconds to soften it a bit before spooning out and then it will make more of a swirl pattern.

Bake for about 30 minutes. Brownies are done when the edges look thoroughly baked and a toothpick inserted in the middle comes out a little fudgy but not totally wet with batter.

Cool completely before cutting into squares and serving