Place all the ingredients - except the strawberries - into a saucepan and simmer over a low heat for an hour or two until it thickens, stirring every now and then. When the sauce cools, it will thicken up further, so keep this in mind.
Whilst the sauce is thickening, place the strawberries onto a baking tray and bake at 350F/180C for around 30 minutes or until soft and the outsides are beginning to caramelise.
When the strawberries are roasted and the sauce is thick, place the fruit into the saucepan and use a hand blender to process until there are no more lumps.
Leave the sauce to cool and store in the fridge in an air-tight container.