Start by making the “rice”. Combine the sunflower seeds, salt and 2 cups (450ml) of water in a small bowl, and soak for at least 4 hours, or overnight. Then drain and rinse well.
Put the sunflower seeds in a food processor and pulse to finely chop—do not overprocess or you’ll end up with sunflower butter! Transfer the sunflower seeds to a large bowl. Do not clean the food processor.
Peel and roughly chop the parsley root. Put it in the food processor, along with the lemon juice and some salt. Pulse to mince the root into “grains” about the size of rice. Add it to the bowl of sunflower seeds and fold to combine. Season with more salt if desired.
Put a sushi mat (or a piece of plastic wrap) on a clean cutting board with the slats running horizontally. Put a sheet of nori, shiny side down, on the mat, 3⁄4 inch/2cm from the edge closest to you. Using damp hands, spread a thin layer of the “rice” evenly over the nori sheet, leaving a 11⁄4–inch- / 3cm-wide border along the edge farthest from you. Arrange about one-fifth of the kale, beetroot, carrot, spring onions, and avocado strips horizontally across the centre of the rice, and then sprinkle with sesame seeds.
Use your thumbs and forefingers to pick up the edge of the mat closest to you. Use your other fingers to hold the filling while you roll the mat over to enclose it. Gently pull the mat as you go to create a firm roll.
Continue rolling until all the “rice” is covered with the nori and you have a neat roll. Shape your hands around the mat to gently tighten the roll. Use a wet sharp knife to cut the roll into 5 or 6 pieces.
Repeat the process, using up all the ingredients. Arrange the sushi on a serving platter and serve with the white miso ginger sauce.
To make the sauce, combine the miso, vinegar, oil, ginger, and maple syrup in a small bowl. Whisk to blend. Store leftovers in an airtight container in the fridge for up to 1 week.