Place the beef in the freezer for about 1 hour to firm it up.
Using a very sharp knife, slice the meat very thinly.
Place the slices between two sheets of parchment paper. Gently flatten with a rolling pin until evenly sliced.
In a bowl, whisk together the old-fashioned mustard and a drizzle of olive oil.
Add the arugula and toss to coat.
Place the beef slices on plates. Season with salt, a drizzle of olive oil, and a squeeze of lemon juice. Top with the dressed arugula, then garnish with Parmesan cheese and pine nuts.
