Once the meat is tender, remove it from the pot and keep it covered with a plate so it doesn't dry out. Let the liquid in the pot keep simmering - you should end up with about half a litre. Remove the spice bag just before thickening the sauce with the roux. Melt about four tablespoons of butter.

In the butter, sauté the remaining two roughly chopped onions until nicely golden. Just before they're done, sprinkle in two to three tablespoons of cane sugar and let it dissolve.

Finally, stir in plain flour - enough to form a thicker paste, the roux. Whisk vigorously for a moment, then gradually stir it into the bubbling liquid in the pot where the meat was braised.

Mix thoroughly - you can even whisk it well. Add tomato purée or canned tomatoes. Stir again and simmer gently for about 20 minutes.

Blend the simmered sauce with a hand blender until completely smooth. Then strain and push it through a fine sieve. Give it one last taste and adjust the seasoning with a pinch of salt, sugar, pepper... whatever it needs.

There's one more trick to turn this smooth sauce into a truly velvety one. Simply whisk a piece of chilled butter into the finished sauce once it's off the heat.

Return the meat to the sauce, warm it through, and serve.

Try adding a couple of cloves for extra flavour. The sauce will taste a touch sweeter, but delicious! If you're making the sauce for meatballs, add in the drippings from frying or baking the meatballs too. Even the browned bits of the meat mixture will add extra flavour to the sauce.