Begin by Making Relish:

Toss all the relish ingredients in a medium bowl, except for the onion and the egg white and yolk. (The egg will become “stained” by the balsamic vinegar, so it is added to the relish lasSet aside until fish is ready.

Prepare Potatoes and Onion:

Skewer the potatoes onto 4 or 5 skewers and place them onto a sheet pan covered with foil. Skewer the onions (through their thickest parts, the root ends will help hold them togetheand place them on the sheet pan along with the potatoes. Brush all the potatoes and onions with olive oil on all their sides, then sprinkle them generously with salt and freshly ground pepper. Set aside until grill is ready.

Prepare Grill:

If using charcoal, light coals and build up a medium-high fire that will last 30-40 minutes. If using a gas grill, turn in on at medium-high and allow to fully heat.

Grill Potatoes and Onions:

Beginning with the onions, grill them until they are slightly blackened and beginning to soften. Set them onto your sheet pan and cover them with a second piece of foil to help them stay warm. Grill potatoes until they are nicely browned and fully heated inside. Place them onto the sheet pan and cover them with foil. Once onions have cooled a bit, remove them from the skewer, cut off their root ends and chop them. Add the onions to the relish. Place the potatoes in a covered bowl so they stay warm.

Prepare Tuna and Haricots Verts:

Heat a large pot of generously salted water to a boil. Reduce heat to a simmer and keep ready for cooking the haricots verts. While the potatoes and onions are grilling, place the tuna portions onto a sheet pan with two layers of foil. Brush the tuna on both sides with olive oil then sprinkle generously with salt and freshly ground pepper. Cook the haricots verts in the simmering water until they are just tender and still bright green. Drain them and toss them with the butter and a little salt and pepper. Cover them with a lid so the stay warm.

Grill and Serve Tuna:

Last, check the grill to see that it is still at least at a medium heat level (tuna does cook quickly). Next, place the tuna portions onto the grill and remove top layer of foil. Discard used foil. Grill tuna on both sides for just 3-4 minutes per side so that the tuna remains pink/rare in the middle.

While tuna grills, add the egg white to the relish. As soon as tuna is done, remove it to the sheet pan with the second (clealayer of foil. Quickly place 5 baby potatoes and a small bunch of haricots verts onto each of 6 serving plates. Place the tuna portions onto each plate, top with a generous spoonful of the relish. Last, sprinkle the plates with the grated hard cooked egg yolk and serve immediately. Makes 6 servings.