In a large bowl, beat the softened butter, brown sugar and granulated sugar together for 2 to 3 minutes, until light and fluffy.

Mix in the sourdough discard until fully incorporated.

Add the eggs one at a time, mixing well after each addition.

Stir in the vanilla extract. The mixture should look thick and creamy.

In a separate bowl, whisk together the flour, baking soda and salt.

Gradually mix the dry ingredients into the wet mixture until just combined. Do not overmix.

Fold in the chocolate chips by hand.

Cover and refrigerate the dough for at least 1 hour, or 2 to 3 hours for extra thick cookies.

Preheat the oven to 350°F (175°C) and line baking sheets with parchment paper.

Scoop large dough balls of about 3 tablespoons each, keeping them tall rather than flattened.

If desired, press chopped chocolate pieces on top of each dough ball.

Bake for 11 to 14 minutes, until the edges are golden and the centres still look slightly soft.

Let the cookies cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.