Two hours before grilling, remove the provolone cheese from the refrigerator and let sit at room temperature. Letting the cheese sit out in the air will allow the cheese to form a crust and make it easier to grill.
Preheat the grill to medium-high direct heat, leaving some space for indirect cooking.
Grill the chorizo, turning occasionally, until nicely charred and hot inside, about15 minutes. Chop roughly and set aside.
Heat a griddle over the direct heat. Lightly brush the top of the cheese with canola oil and season with salt and pepper. Place on the griddle, seasoned-side down, and cook until the cheese is dark golden brown and crusty, about 5 minutes. Brush the top lightly with oil, season again, carefully flip over and move the griddle to the indirect heat. Continue cooking until the bottom begins to turn light brown and the cheese is melty, covering if need be. Remove to a plate and sprinkle with the oregano and red pepper flakes.
Brush the bread on each side with some olive oil and sprinkle with salt and pepper. Grill over direct heat for about 1 minute per side-the bread should be crisp and a bit charred outside, but chewy inside.
Heat a griddle or cast-iron skillet over medium-high heat. Add the butter and melt. Crack the eggs into the skillet, sprinkle with salt and pepper and cover with another pan. Cook until the whites are set and the yolks still runny, about 3 minutes.
While the eggs cook, whisk together the vinegar and mustard in a large bowl and season with salt and pepper. Slowly whisk in 1/2 cup olive oil until emulsified. Taste and whisk in the honey if desired. Put the rocket, tomatoes and onions in a large bowl and season with salt and pepper. Drizzle some vinaigrette around the sides of the bowl and gently toss to coat.
To serve: Smear some cheese on the toasted bread. Top with an egg, chopped chorizo, a drizzle of olive oil and parsley leaves. Serve each crostini with some rocket salad.