I'm on a prosciutto, burrata, and arugula kick lately. I recently had the most amazing prosciutto, burrata, and arugula salad at one of my favorite restaurants and I haven't been able to take my mind off the three ingredients since. These crostinis are my interpretation of that fateful dish, with the much drier mozzarella standing in for its creamy counterpart.
To make the dressing, whisk together the mustard, lemon juice, balsamic vinegar, salt, and pepper in a small bowl. Slowly whisk in the olive oil until the dressing is fully emulsified. Toss with the arugula in a medium-sized bowl and set aside.
Preheat the oven to 350 degrees.
Brush one side of the baguette slices with olive oil and season with salt and pepper, to taste. (I found it was easiest to pour ¼ cup of olive oil onto a plate and dip the slices into it.) Lay the baguette slices on a baking sheet and toast in the oven until slightly golden brown, about 5 minutes. Remove from the oven and top each slice with the mozzarella slices, fitting 2-3 onto a slice at a time. Turn the oven to broil on high and broil the baguette slices until the mozzarella is melted and the baguettes are golden brown, about 3 minutes.
To assemble, top each baguette slice with ½ piece of prosciutto and then the arugula.