Heat oil in a saucepan over medium-high heat. Cook onion for 3 minutes. Add garlic and cook for 1 more minute. Add beer and continue cooking for 5 minutes, or until liquid is reduced by half.

Add brown sugar, rice vinegar, ketchup, hoisin sauce, and harissa sauce. Cook 20 minutes over medium-low heat, stirring occasionally, until sauce thickens. Set aside half the sauce to serve with steaks.

Brush both sides of steaks with two-thirds of remaining sauce. Refrigerate for 30 minutes.

Preheat barbecue to medium-high.

Remove steaks from fridge 15 minutes before cooking. Place steaks on oiled barbecue grill and cook 7 to 8 minutes per side, or until internal temperature reaches 70°C (160°F) for medium doneness. Use remaining third of the sauce to brush on steaks while cooking.

Remove steaks from heat, cover with aluminum foil and set aside for 10 minutes.

Serve steaks with the sauce, and grilled slices of sweet potato and asparagus.