Preheat oven to 350°F (175°C). Grease and flour a 9x13 inch baking pan.

In a large bowl, whisk together the flour, sugar, baking powder, baking soda, and salt.

In a separate bowl, combine the melted Biscoff cookie butter, milk, oil, eggs, and vanilla extract. Mix well.

Pour the wet ingredients into the dry ingredients and mix until just combined. Do not overmix.

Pour the batter into the prepared baking pan and bake for 30-35 minutes, or until a wooden skewer inserted into the center comes out clean.

Let the cake cool in the pan for 10 minutes before inverting it onto a wire rack to cool completely.

In a large bowl, cream together the softened butter and Biscoff cookie butter until light and fluffy.

Gradually add the powdered sugar, beating until smooth. Add the milk and mix until the frosting reaches your desired consistency.

Frost the cooled cake with the Biscoff cookie butter frosting.