To make the roast cosmo mix, preheat your oven to 200°C/gas mark 6. Put the bone marrow on a baking tray, season with salt and pepper and add a couple of rosemary sprigs. Cook in the oven for 20–25 minutes, or until the marrow is cooked through. Remove from the oven and let it rest for a few minutes.

Meanwhile, prepare your homemade water bath. Pour water two-thirds of the way up the sides of a deep saucepan or wok (better) and place over a medium heat. Do not let the water boil, as this will damage the quality of the alcohol (you want it at a constant 60°C).

Put the vodka and Triple Sec into a large ziplock freezer bag and add the roasted bone marrow complete with the herbs and any juices. Seal the bag, removing as much air as possible and making sure no sharp pieces of bone can tear it. Put the bag into your water bath and leave for 45 minutes, then remove and place on a tea towel to dry. Transfer the mix to a non-reactive container, seal and place in the freezer for 2 hours.

When you take it out of the freezer you will notice that the freezing process has made the bone marrow fat separate and solidify, allowing the alcohol to be filtered off cleanly and clearly. Line a funnel or sieve with two-fold muslin (a coffee filter or tea towel works well too) and put it on top of an empty glass jar or deep container. Remove the marrow pieces first, then strain the liquid through the muslin – this process will take up to 30 minutes. When ready, put a lid on and reserve.

To make your Roast Cosmo, shake all the ingredients except the garnish with ice cubes and double strain into a chilled glass. Garnish with a lime wedge or zest.