Put the rice in a small bowl, cover with cold water and massage the grains with your hands to remove the starch. Drain and repeat the process until the water runs clear.
Put the rice in a small saucepan with a tight-fitting lid. Cover with 2.5cm of cold water, put the lid on and simmer over a medium heat for 10 mins. Take off the heat and leave with the lid on for a further 15 mins. Stir through the vinegar, then leave to cool completely.
Fill a small bowl with cold water and lay out a sushi mat (about £1 from any large supermarket). Place a nori sheet, shiny-side down, on top of the sushi mat. Spread a quarter of the rice onto the nori, leaving a 1cm border at the top.
Put a quarter of the chilli and carrot in a line at the bottom of the rice. Place a quarter of the cucumber and mackerel in a strip along the centre.
Dampen the top border with a little water to help seal the roll. Fold the bottom edge of the seaweed over the first line of the filling, then use the sushi mat to roll up the maki. Repeat to make four rolls. Using a serrated knife, cut each roll into eight rounds. Serve with soy sauce for dipping. Want a little help with this recipe? Watch our how to make sushi video.