The Ultimate Steak Sandwich Recipe | Say Mmm

Ingredients

• 1/2 stick unsalted butter
• 3 heaping tablespoons all-purpose flour
• 2 cups whole milk
• 2 cups grated Gruyere
• Kosher salt and freshly ground black pepper
• 1 tablespoon prepared horseradish
• 1 bunch baby arugula
• 1/2 lemon, juiced
• 1/2 cup mayonnaise
• 2 soft hoagie rolls
• Extra-virgin olive oil
• 1/2 pound rib-eye, finely sliced
• 1 large fennel bulb, fronds removed and halved
• 3 heaping tablespoons sour cream
• 1 bag coleslaw mix
• 2 tablespoons chopped fresh tarragon leaves
• 2 tablespoons chopped fresh flat-leaf parsley
• 1 tablespoon extra-virgin olive oil