Slowly drizzle in the oil. Season to taste.
Place the red onion in a bowl, add lemon juice, olive oil and sumac and let sit for 10 minutes. Toss the other ingredients through.
Preheat the oven to 180°C.
Place all the ingredients in a bowl except for the feta and chutney. Mix to combine and roll into walnut-sized balls. Make a hole in each ball, push a small cube of feta into the centre and close up. Place on a baking tray and toss in a little oil.
Bake for 10 minutes. Remove from the oven, roll in some chutney or chilli jam, and return to the oven for 5 minutes to glaze.