Heat oven to 200C/180C fan/gas 6. Boil the potatoes for 10 mins until mostly tender, drain and leave to steam dry. Toss the potatoes in a large roasting tin with the garlic, drizzle over 1 tbsp oil and season. Roast for 20 mins.
While the potatoes are roasting, squeeze half the lemon juice over the shallot and half of the kale, season, then massage gently to encourage the kale to soften.
Remove the garlic cloves from the oven. Put the rest of the kale on top of the potatoes, drizzle over a little oil, season and return to the oven for 5 mins until crisp.
Meanwhile, blitz the garlic, avocado, mustard, remaining oil and lemon juice together, add enough water to create a smooth dressing and season to taste. Mix the potatoes and cooked kale into the raw kale salad and tip onto a platter. Drizzle over the dressing, then top with the feta, chilli flakes and pumpkin seeds.