Start with a very sharp knife and a clean cutting board. Ensure your Wagyu beef is partially frozen; this will make it easier to handle and chop finely. Dice the beef into small cubes and then continue to chop until it reaches the desired consistency. Alternatively, you can ask your butcher to mince it for you.

In a mixing bowl, combine the finely chopped Wagyu, capers, Dijon mustard, minced shallot, chopped cornichons, and fresh parsley. Mix gently until well combined.

Drizzle in the olive or truffle oil and mix again. Season with salt and pepper to taste.

Transfer the tartare to a serving dish. If you'd like, create a small well in the center and place the egg yolk in it.

Serve immediately with toasted baguette slices or crackers.