^ Yes, fresh chillies add some spark. Also try some worcester sauce, roasted cumin seeds and a few bay leaves.
Brown the beef, let it rest, sweat an onion and some carrots, return meat to the pan, add flour, season, pour over stock, add thyme/bay/oregano, add gravy browning and Worcestershire sauce, slow cook in the oven for a few hours.
Whole grain mustard, cumin and Guiness all sound promising, not at the same time obviously. It can't be too spicy though. One of the people I'm cooking for can't handle anything spicy at the moment.
Use Guinness/real ale in there, as Dolph says a whole bottle. Try adding something a bit different to the sauce like mushroom ketchup or even a little nutmeg as well as mixed herbs. To make it a little different when serving: thickly slice part of a a french stick. Liberally spread one side of each slice with dijon/french mustard. 15 minutes before the end of cooking take the lid off the stew/casserole, place the bread mustard side up on top of the stew and bake in the oven for 15 mins. When it's ready the gravy will have soaked into the bottom of the bread and the top of the bread will be all mustardy and crunchy....yum!
