Step 1 Preheat oven to 200°C. Steam potatoes and parsnips for 10 minutes, until tender. Drain.
Step 2 Meanwhile, combine breadcrumbs and mince in a large bowl. Finely chop 1 of the onion halves. Add to mince, along with egg and half the mint. Using clean hands, mix until well combined. Shape into 12 meatballs.
Step 3 Slice remaining onion halves into wedges. Spray a large ovenproof dish with oil and add meatballs, potatoes, parsnips and onion. Spray with oil. Cook for 25–30 minutes, turning once halfway through cooking.
Step 4 Add tomatoes in the final 5 minutes of cooking. Garnish with mint before serving.
Make double the number of meatballs. Freeze extra meatballs to use later in the week in pasta dishes or serve with gravy.
