Clam Chowder Shell Pasta

Name: Clam Chowder Shell Pasta
Ingredients: 4 slices bacon, cut into 1/4-inch pieces; 1 tablespoon butter; 0.5 cup diced onion; 0.25 teaspoon kosher salt, or more to taste; 1 tablespoon all-purpose flour; 1 (6.5 ounce) can whole clams; 1 (6.5 ounce) can minced clams; 1 (8 ounce) bottle clam juice; 1 (8 ounce) package shell pasta; 0.5 cup peeled, diced Yukon Gold potatoes; 0.333 cup diced celery; 1 sprig fresh tarragon; 1 pinch cayenne pepper, or to taste; 0.5 cup heavy cream; 1 tablespoon finely chopped Italian parsley, or more to taste; 2 tablespoons freshly grated Parmigiano-Reggiano cheese, or more to taste