In a large heavy based saucepan heat the oil and butter together over a medium heat.
Add the onions and cook for around 5 minutes, keep stirring so they don’t stick.
Add the celery salt and a good grind of pepper, the Worcester sauce, garlic and thyme sprigs and cook for around 20 minutes, or until the onions caramelise.
Meanwhile mix together the yogurt and cream cheese in a bowl.
When the onions are browned and cooked, discard the thyme sprigs and mix the onions into the yogurt.
Check the seasoning and adjust if needed. Serve with crackers or crisps.
*All information included in this recipe has been provided by Onken.