SLABS BEEF ROAST and English Mustard huge crisps - surely the Daddy of Beefy savoury crisps!.. Is there anything more British than Crisps flavoured with English Mustard? Nope! Fabby SLABS, you've done it again, Beef Roast & English Mustard is a stunner! this is an indulgent treat, made with our own blend of sunflower oil and olive oil, the best seasoning, all in all, a super-duper potato crisp. We Love Crisps.