Wrap the potatoes separately in foil. Charcoal/gas/electric grill: Cover and grill the potatoes over/on a low heat (approx. 150 °C for approx. 1 hr.
Combine the balsamic, oil and syrup, coat the meat with the mixture, cover and marinate in the fridge for approx. 30 mins.
Heat the oil in a pan. Sauté the shallot and tomatoes. Add the lemon juice, syrup and cumin, bring to the boil, cook on a rolling boil for approx. 5 mins., leave to cool. Stir in the parsley.
Charcoal/gas/electric grill: Grill the entrecôtes over/on a very high heat (approx. 250 °C for approx. 2 mins. on each side, season with salt.