Chop up the butter into chunks and place in a large mixing bowl. Beat using an electric mixer or wooden spoon for 1 minute. You want the butter to be slightly softer, broken up, but not at the 'creamed' stage.

Add the light brown sugar and white caster sugar and beat together until just combined. Try not to over-mix at this stage otherwise the butter will become too soft.

Mix in both of the eggs. The mixture won't look very appealing at this stage but don't worry it will do soon!

In a separate bowl, stir together the self-raising flour, plain flour, salt and baking powder until well mixed. Tip into the butter mixture and fold everything together until it forms a thick cookie dough.

Now add all of the chocolate chips and use your hands to mix them into the dough.

Line a baking tray or tin (one that will fit inside your freezer) with greaseproof paper.

Weigh out 120g of the cookie dough, then use your hands to roughly shape it into a ball and place it on the baking tray. Thick cookies are meant to look rustic, so lumps and bumps on the cookie dough is exactly what you're looking for.

Repeat this step until all the cookie dough is used up. You should get between 9-10 cookies in total. At this stage, you don't have to worry about the cookies being too close together on the baking tray. As long as they're not touching it's all good.

Cover the baking tray with clingfilm and freeze the cookie dough balls for at least 90 minutes or up to 48 hours for best results. The longer you leave them, the thicker your cookies will be.

Whilst the cookies are in the freezer, preheat your oven to 180°C (fan).

Do this step 5 minutes before the freezing time is finished:Line a large baking tray with greaseproof paper and place in the oven for 5 minutes to heat up. The heated tray will help the cookies crisp up and brown on the outside but still keep a gooey centre.

Place 3 to 4 of the frozen cookie dough balls onto the tray. These cookies are very chunky so make sure you leave plenty of room between them.Bake the cookies in batches if you need to.

Bake on the middle shelf of your oven for 15 minutes until golden on the outside edge but still only lightly browned on the top and in the middle. The cookies should still be nice and thick, with very little spread.

Leave to cool for 5 on the baking tray, or just until you're happy to pick them up without them falling apart.

Enjoy your cookies straightaway!