Heat 15 ml of olive oil in a saucepan over medium heat. Add the finely chopped shallot and sauté for about 5 minutes until it becomes soft and translucent.
Add the brown sugar to the pan and stir until it begins to dissolve. Add the plum and apricot wedges and continue stirring until the sugar is fully melted and coats the fruit pieces.
Pour in the beef stock, mirin, and red wine vinegar. Add the star anise and orange slices to the pan. Stir well to combine all the ingredients.
Lower the heat to medium-low and simmer the sauce for about 15 minutes, stirring occasionally. Allow it to thicken and for the flavours to meld together. If you prefer a thicker consistency, continue to simmer for a few more minutes until it reaches your desired thickness. Remember it thickens further as it cools, so stop while it still looks slightly loose. Alternatively, you can blend the sauce briefly after removing the star anise for a smoother texture.
Once the sauce is cooked, you can remove the star anise and orange slices if you prefer a more refined texture. Alternatively, you can leave them in for added flavour and a rustic presentation. The star anise keeps getting stronger the longer it sits, so take it out if the sauce is not going straight to the table.
Before serving, taste the sauce and adjust the seasoning if necessary. You may wish to add more vinegar for acidity, a pinch of sugar for sweetness, or a little salt for balance.
Once the sauce has the right consistency and flavour balance, remove it from the heat. Set it aside to cool or reheat later as needed. Serve warm with duck, venison, game birds or pork. It keeps 3 to 4 days in the fridge and freezes for up to 3 months, but do not can it: the stock makes it a low-acid sauce.