Preheat the oven to 180°C/350°F (160°C fan). Line 2 baking trays with baking paper.
Place the butter cubes into the Thermomix bowl. Mix for 12 sec/speed 5 until softened. Scrape down the sides of the mixing bowl with a spatula.
Add both sugars to the mixing bowl. Mix for 20 sec/speed 4. Scrape down the bowl thoroughly and mix again for 15 sec/speed 4, until smooth and creamy.
Add the egg and vanilla extract. Mix for 15 sec/speed 3. Scrape down the bowl and mix again for 15 sec/speed 3.
Add the flour, bicarb of soda and salt. Mix for 10 sec/speed 4, scrape down the bowl and mix again for 3 sec/speed 4.
Stir in the chocolate chips by hand with a spatula so they don’t get crushed by the blades. Tip: Transfer the cookie dough to a regular mixing bowl. I find it much easier to scoop and shape the dough this way without the Thermomix blades getting in the way.
Roll the dough into walnut-sized balls and place 5 cm apart on the baking tray. Carefully press a few extra chocolate chips on top (no need to press the dough down). If the dough feels too soft to handle, place it in the fridge for 20 minutes before shaping.
Bake one tray at a time for 12-14 minutes, until golden around the edges but still soft in the centre. Keep the second tray chilled in the fridge while the first bakes.
Leave the cookies on trays for 5 minutes before transferring to a wire rack. They will firm up as they cool.
Notes
To Make Ahead: See my separate blog post on how to freeze cookie dough. Freezing the dough is a great way to always have freshly baked cookies on hand whenever you need them.Storage: Store the cookies in an airtight container for up to 5 days. For longer storage, you can freeze the baked cookies for up to 2 months, just let them thaw at room temperature before serving.