→ For the Shells and Filling
                    
                      
                        01 - 
                        6 ounces jumbo pasta shells (about 25 shells)
                      
                    
                      
                        02 - 
                        Kosher salt, for boiling pasta
                      
                    
                      
                        03 - 
                        8 ounces peeled and deveined shrimp, chopped
                      
                    
                      
                        04 - 
                        1 pound lump crabmeat, picked over for shells
                      
                    
                      
                        05 - 
                        8 ounces dry-packed sea scallops, cut into small pieces
                      
                    
                      
                        06 - 
                        2 tablespoons Dijon mustard
                      
                    
                      
                        07 - 
                        1/2 cup mayonnaise
                      
                    
                      
                        08 - 
                        Dash of Old Bay seasoning
                      
                    
                      
                        09 - 
                        1 medium shallot, minced
                      
                    
                      
                        10 - 
                        Small handful of flat-leaf parsley, minced, plus more for garnish
                      
                    
                      
                        11 - 
                        Freshly ground black pepper, to taste
                      
                    
                  
                    → For the Béchamel Sauce
                    
                      
                        12 - 
                        3 1/2 tablespoons unsalted butter, divided
                      
                    
                      
                        13 - 
                        1 1/2 tablespoons all-purpose flour
                      
                    
                      
                        14 - 
                        1 1/2 cups milk
                      
                    
                      
                        15 - 
                        1 bay leaf
                      
                    
                      
                        16 - 
                        Salt and pepper, to taste
                      
                    
                  
                    → For Topping
                    
                      
                        17 - 
                        1 cup panko breadcrumbs
                      
                    
                      
                        18 - 
                        Extra-virgin olive oil, for greasing and drizzling