Vegetable oil, for frying (about 3 cups)
3 cups lightly crushed salted pretzel rods (about 6 ounces)
3/4 cup all-purpose flour
2 1/2 teaspoons kosher salt, plus more for seasoning
1 1/2 teaspoon freshly ground pepper, plus more for seasoning
2 large eggs
1/4 cup plus 2 tablespoons Dijon mustard
Four 6-ounce chicken cutlets, 1/4-inch thick, pounded if necessary (1 1/2 pounds total)
1 1/2 pounds cauliflower, chopped (1 small head cauliflower)
3 garlic cloves, peeled
2 tablespoons unsalted butter
1/4 cup whole milk, or more to taste
4 cups arugula or baby spinach
1 lemon, halved
Extra-virgin olive oil, for serving