In a large bowl, combine baking soda and Guinness. Add beef, stir to combine. Cover and rest at room temperature for 30 minutes. (Or overnight in fridge).
Place garlic, onion and EVOO into the Thermomix bowl. Chop 4 sec/speed 6. Sauté 5 min/Varoma/speed 1,
Add remaining ingredients, including beef but except carrot and celery. Combine with spatula then cook 60 min/100°C/reverse/speed soft.
Add carrot and celery and continue cooking 30 min/100°C/reverse/speed soft.
Serve with fresh thyme and a side of Colcannon.