Cut the onion on half. Leave the skin on.
Put the beetroot (whole) and the onion in a baking dish. Tuck the garlic between them (with skin on) then add your chosen herb. Drizzle with olive oil, then cover the dish with foil.
Bake in a preheated oven (set to about 190°C) for 30-40 minutes, until you can easily push a skewer through the beetroot. Let it cool, then refrigerate until you’re ready to bake the tarts, or continue with the recipe now.
Remove the skin of the beetroot and onion, then slice them thinly. Remove the skin of the garlic and mash the flesh into a paste (you can add the cooking jus or a drop of oil to this)
Unroll the puff pastry onto a large chopping board. Using a fork, prick the pastry a few times, then spread the garlic paste onto it.
Layer the beetroot and onion onto the pastry, leaving a border. Crumble over the goat’s cheese and scatter with the walnuts. Fold up the edges of the pastry slightly to create a rim.
Season with ground black pepper and drizzle with the honey or maple syrup.
Bake for about 20-25 mins, or until the pastry is golden.
Cool for a couple of minutes, then serve.