Combine the mustard, olive oil, red wine vinegar, maple syrup in a container or tray large enough to hold the ribeye. Stir well to combine.
Place the pork into the marinade and allow to soak in the flavours for at least 2 hours, preferably overnight.
Heat the BBQ to a medium-high heat.
Lift the pork out of the marinade and allow it to drip off the meat, not cleaning it down. You want some of the marinade to stay on there to get the beautiful char when it hits the heat.
Season the pork well with salt and pepper, before putting it onto the BBQ.
Cook the pork until well browned/beginning to char and turn. Cook evenly on all sides. Once nicely charred, you have 2 options. If your BBQ has a non-contact section, you can move the pork to this part of the BBQ, put the lid on and allow it to cook through for 45 minutes to an hour turning frequently. If your BBQ does not have a part where non-contact cooking is possible, move it into your oven. Set it to 180 degrees celsius and allow to cook for 45 minutes to an hour, until firm to touch in the centre with a little bounce. If you have an internal thermometer you should cook it to around 68 degrees celsius.
Allow to rest for at least 20 minutes.
Slice and serve alongside a generous serve of chimichurri and BBQ sauce.
Place all ingredients, apart from the olive oil and red wine vinegar, into a food processor or blender and blitz until chopped and combined. If you do not have a food processor/blender that will do this job, then you can easily do it yourself. Just finely dice with a knife.
In a bowl, combine the herb mix with the olive oil and red wine vinegar and mix to combine.
Taste and season with salt and pepper.
Serve right away, or store in an air-tight container or jar in the fridge. If refrigerating, allow to come to room temperature before serving.