A sustainable steakhouse - now there's a 21st-century concept. Take the family-style grill and beef it up with green, clean credentials that will appeal to diners with a conscience.

First, flame up steaks with a provenance to rival an Aboriginal painting. Then roast chickens with organic certification stamps and slow-cook lamb grazed on saline pastures. Add a wood-fired oven and a tapas bar and you've pressed all the buttons.

There's so much to admire about MuMu Grill: the wood-grain profiles on the walls, the pine sheets stencilled with hearts, cows and pigs, the George Nelson-style bubble lamps suspended from the ceiling, the handsome kitchen.

Then there is the heartfelt manifesto - which hangs near the front door and in the toilets - about eating grass-fed beef and food grown in a sustainable manner. And the menu's details about the origin of the beef, whether it is from King Island, the Hunter Valley or Longford in Tasmania.

But there are also things to wonder about. Why, for instance, can't we get a table at the time we want? When we show up earlier, by accident, the restaurant is barely a third full. Why doesn't our good-natured waitress know anything about the jamon and sherries listed on the blackboard above the bar?

Still, I manage to score a bone-dry white La Goya manzanilla sherry while we snack on some home-made corn bread. (Not recommended: damp and lifeless despite the corn kernels embedded in the loaf.)

Around us, the room is relaxed. Families here, couples there. Near the kitchen, on banquettes, there are a few small groups of four and six.

A few alfresco folk sprawl over trestles and benches in a paved mall shared by cars and pedestrians. The piazza atmosphere would be dreamy on a balmy summer night and is inviting even in the spring air, thanks to the powerful patio heaters.

Our waitress asks whether we are ready for her to "call away" our meals, a thoughtful, if unusual request and it's not long before two beautifully presented main-course specials arrive.

Saltbush lamb "two ways" has a gorgeously thick, grilled backstrap cut into wedges. Next to it are slices of shoulder meat, slowly cooked for hours in the oven. In the middle is a simple pile of pristine mache leaves. A touch of red wine sauce finishes off the dish.

The lamb is wondrous. The meat comes from animals that feed on saltbush, a plant used to reduce salinity levels in dry lands. Leaving aside the possible health benefits (high levels of vitamin E), this meat is rich, moist and clean, with none of the fattiness you find even in spring lamb. The buttery flavours marry brilliantly with the gratin cauliflower.

For the backstrap, a juicy, textured cut not unlike beef but sweeter, the chef's gone for a relish-style accompaniment. His thinking is spot on but I'd like to see brighter, more distinct sweet-and-sour flavours in his chutney.

All thoughts of sharing my dish with my meat-mad companion have flown away (I could have done with more on my plate, to be honest). Fortunately, he's happy with his aged, grass-fed wagyu scotch fillet even though it has come out well done instead of medium rare.

Again, like the lamb, the meat has a clean, lingering and gentle taste, while in the mouth it's both firm and yielding. The steak's garlicky mash and wilted spinach with a wine jus are well-made classics that make the meat the hero of the dish.

A succinct wine list delivers good price points and some good drops and, in true steakhouse style, features martinis as well as Brazilian cocktails and beer.

Classics crop up in the dessert arena, too, with a choice of gingerbread ice-cream sandwich, brown sugar pavlova, chocolate square and sorbets. For those who can't decide, a tasting plate has each of these on board.

However, the rectangular platter is a messy mass of samples. They taste as uniformly ordinary as they look.

It's almost as if all that ambitious goodwill has exhausted itself. Shame, because MuMu Grill is right in so many respects.

This smart, modern take on the traditional steakhouse is sorely needed in Sydney. And the restaurant proves that animals that have had good lives produce glorious-tasting meat which justifies their end.