To begin, soak the barley groats in cold water for one hour to soften. Drain thoroughly before use. Meanwhile, preheat your oven to 180°C (fan assisted) or 200°C (conventional). Prepare natural sausage casings by rinsing them under cold water and soaking them for 15 minutes in lukewarm water.

In a large mixing bowl, combine the minced pork belly, diced pork fat, grated onion, and drained barley groats. Mix thoroughly using your hands to distribute the fat evenly, this helps achieve the traditional dense texture without breaking the casing.

In a separate bowl, stir together the pig’s blood, rye flour, salt, allspice, and black pepper. Whisk gently until fully combined. Avoid whipping air into the blood, maintain a smooth and steady stir to preserve the sausage’s deep, rich colour.

Slowly pour the blood mixture into the pork blend. Mix gently but thoroughly by hand until all ingredients are well incorporated. The filling should be cohesive and thick but pourable, adjust with a touch more rye flour if too runny.

Using a sausage stuffer, carefully fill the soaked casings with the mixture, avoiding air pockets. Twist the sausages into links roughly 15–20cm long. Do not overstuff, leave room for expansion during cooking to prevent bursting.

Bring a large pot of water to 80°C (not boiling). Gently poach the sausages for 20–25 minutes. Keep the temperature below simmering, this step sets the shape and texture without cooking the sausage fully.

Remove the sausages from the water using a slotted spoon and place them on a wire rack to cool slightly. This resting period helps the casing firm up and allows excess moisture to escape.

Transfer the sausages to a baking tray lined with parchment paper. Roast in the preheated oven for 45 minutes, turning once halfway through. They should be dark brown and crisp at the edges while retaining a soft centre.

Allow the sausages to rest for 5 minutes out of the oven before serving. This prevents the casing from tearing when sliced and lets the flavours settle fully into the meat.

Serve the mustamakkara hot, sliced thick, alongside a generous spoonful of lingonberry jam. For a traditional Finnish touch, pair it with rye bread or boiled potatoes. The tang of the berries balances the richness beautifully.