Heat your oven to 220°C (428°F) then peel the potatoes.
Sit one potato in a tablespoon, holding it firm, and use a sharp knife to make parallel cuts, around 2-3mm apart, working your way from one end of the potato to the other. The spoon prevents you from slicing right through the potato; for tiny potatoes use a teaspoon. Repeat until you’ve done all potatoes then transfer them to a baking pan.
In a microwave or small pan, melt the butter then stir in the salt, garlic powder, onion powder, paprika and cumin until well combined. Dip a silicone pastry brush into the spiced butter and brush all sides of each potato, ensuring it seeps into every groove of the potatoes.
Bake for 45 minutes — longer if you prefer the potatoes crispier and darker than pictured — brushing them every 15 minutes with the spiced butter from the bottom of the tray..
When the potatoes are to your liking, use tongs to transfer them to an oven-proof serving plate. Pour the melted spice butter into a dish. Return the potatoes to the oven, turned to low until you’re ready to serve.
Combine the fresh herbs with the melted spiced butter and a tablespoon of extra virgin olive oil and brush on just before serving. Sprinkle with sea salt or chilli salt.