Split the mince mixture into 8 evenly sized balls.
Take one ball of mince and press it flat inside the forming ring (or by hand) to create a disc about 1cm (½ inch) thick with a shallow indent in the centre. Remove the ring and set this disc aside.
Press another piece of mince into your now-empty forming ring on a new piece of foil.
Spoon 15g (about 1 tablespoon) of chilled garlic butter into the centre indent, keeping the butter away from the edges so you have room to seal.
¼ cup garlic butter
Place the first piece of mince on the other piece with the garlic butter like a sandwich. Seal the edges to make sure the butter doesn't run out when you start cooking.
Repeat steps 3 to 6 until you have 4 complete burger patties. Then, you can pop the patties on a plate and refrigerate them until you are ready to cook them.
Make sure the pan is heated to medium-high heat (around 200°C / 400°F surface temperature), and cook the patties 2 at a time. Add a little butter to grease the pan if necessary. Cook for 5–6 minutes per side over medium-high heat until the internal temperature reaches 160°F / 71°C. Avoid pressing down on the patties — this will rupture the butter pocket.
1 tablespoon butter
Rest the patties for 5 minutes before serving. The molten garlic butter inside will be extremely hot straight off the pan — the rest allows it to cool slightly and redistribute through the meat.
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Notes
Storage: Refrigerate uncooked stuffed patties covered on a plate for up to 24 hours — the salt will start drawing moisture from the meat beyond that. Store cooked patties in an airtight container in the fridge for up to 3 days.Freezer-friendly: Freeze uncooked patties on a flat tray until solid, then transfer to a zip-lock bag for up to 2 months. Thaw overnight in the fridge before cooking.Reheating: Warm cooked patties in a covered pan over low heat with a splash of water, about 3–4 minutes per side. The butter pocket won't be as dramatic but the patty stays flavourful.Pro tip: Chill the garlic butter until very firm before assembly — soft butter is nearly impossible to seal inside the patty and will leak during cooking. Run your thumb around the sealed seam a second time to ensure there are no gaps.No forming ring? Shape each half into a flat disc about 1cm (½ inch) thick by hand. Make a shallow thumb indent in the centre of one disc, add butter, top with the second disc, and pinch the edges firmly.Substitutions: Swap garlic butter for herb compound butter (parsley, thyme, lemon) for a fresher flavour, or use a small nugget of firm blue cheese for a steakhouse-style stuffed burger. Black pepper works in place of white pepper for a sharper bite.