Making a beef stew in the slow cooker but I’ve forgotten to get onions 
If I substitute leeks instead will it be ruined?
Would be going in with braising steak, carrots and swede, to be served with mashed potatoes in a giant Yorkshire pudding.
Shops don’t open til 10am and we’re going out at 9.30.
Please help, I’ve been looking forward to this dinner all week 🙈