Preheat your oven to 200C; line a tray with a silicone mat.
Cut the potatoes into wedges & par boil for 5 mins. Pull them out of the water onto the tray & dunk the green beans in the water for 1 min. Drain & leave to steam dry.
Toss the potatoes with 1 teaspoon of avocado oil, season & roast for 15 minutes.
Meanwhile finely dice the fennel & fronds & spring onion, add to a large bowl with the nigella seeds, oregano & chilli flakes.
Toss the potatoes around then add the beans, return to the oven for 10-15 more minutes until the potatoes are crisp & the beans are tender. Toss straight into the bowl & add 1/2 the dressing. Let everything infuse then add the sauerkraut & mix through.