Marinade the steak overnight with a handful of ground physalis, mustard, lemon juice, salt and pepper.
To prepare the jam, mash the physalis with a hand blender with water and heat in a pot with sugar, vinegar, salt and pepper. Allow to reduce to half, stirring constantly, and set aside.
Put the steak on a grill over high heat 10 minutes per side and season with salt and pepper to taste.
Serve with physalis jam spread.
