Heat 1 tablespoon of oil in a fry pan to high heat, add half of the beef and cook, turning, for 5-6 minutes or until browned; season to taste. Transfer to a plate. Repeat with 1 tablespoon of oil and remaining beef. Transfer to a plate.
In the same fry pan, add onion, garlic, mustard seeds, spice, coriander and pearl barley. Cook, stirring, for 3-4 minutes or until onions have softened and spices are fragrant. Scatter over corn flour and cook, stirring, for a further 1 minute.
Place the browned beef, onion, garlic, mustard seeds, spice, coriander and pearl barley into the slow cooker. Stir in stock, chipotle chillies, parsnips, vinegar and maple syrup. Cover with lid and cook on low for 8 hours.
Divide Beef Barbacoa among plates. Serve with barbecued corn, asparagus, tortillas and lime wedges.
Chipotle chilli in Adobo sauce is available from selected supermarkets and specialty food stores. You can substitute with Chipotle BBQ Sauce available from super markets or barbecue sauce.
Barbacoa is traditionally slow cooked over coals then shredded down and tossed through its cooking sauce. With this recipe we have left the meat as is, in chunks, to serve as a wholesome slow cooked meal. If you have left over, shred to use in wraps and salads or alternatively serve on rice.