Step 1

Preheat the oven to 180C / 350F and line an 8 1/2 x 8 1/2 inch tin with greaseproof paper.

Step 2

In a medium bowl or jug, mix the Guinness, cornstarch, vanilla, vinegar and oil together.

Step 3

In another larger bowl, mix the rest of the ingredients, except for the chocolate chips.

Step 4

Slowly stir the wet ingredients into the dry with a wooden spoon.

Step 5

Stir in half the chocolate chips.

Step 6

Spread the mixture into the tin and top with the rest of the chocolate chips.

Step 7

Bake for 25-30 minutes until a fork or toothpick inserted into the middle comes out clean.

Step 8

Make sure to allow them to cool before serving as they will be gooey! I like to refrigerate mine for a bit to firm up before slicing into 9 squares.

Step 9

Serve and enjoy! Keep for up to 3 days in an air-tight container.