On a cutting board chop together the anchovy fillets, garlic, and pinch of salt. Using the side of the knife blade mash the garlic and fillets into a paste, then scrape into a medium bowl. See Notes below if using anchovy paste.
Whisk in the egg yolk, lemon juice, mustard, and Parmigiano Reggiano.
Using a Hand Whisk: Starting with a few drops slowly whisk in the olive oil and whisk until all the olive oil has been added and the dressing is glossy.Using an immersion Blender: Placing the blender in the bottom of the medium bowl turn it on a low setting and slowly stream in the olive oil until all the olive oil has been added and the dressing is glossy. The blender will also help break down the garlic and anchovy fillets into a finer paste.
Fold in the lemon zest, then add additional salt to taste.
Notes
1. Anchovy paste can be substituted for anchovy fillets. One anchovy fillet is equivalent to 0.5 teaspoons of anchovy paste.2. If substituting anchovy paste, combine crushed garlic, salt, and anchovy paste in a small bowl, then work them all together into a uniform paste prior to proceeding to step 2 in the recipe.3. A mortar & pestle can also be used to mash the anchovy fillets, garlic, and salt instead of the side of a knife.4. You can secure the bowl with a damp towel rolled up and wrapped around its base to help prevent it from slipping.5. The number of servings will vary based on the application.6. Since this is made with fresh ingredients you can expect it to last 3-5 days if stored in an airtight container in the refrigerator.7. Besides your favorite salad, this dressing can also be served as a dressing for wraps, sandwiches, and burgers.8. Nutritional information: The nutritional information is only an estimate. The accuracy of the nutritional information for any recipe on this site is not guaranteed. The nutritional value is only for the dressing and does not include the nutritional value of anything served with the dressing. It does not include the nutrition for any substitutions.9. Be sure to check out the Key Ingredients along with the Recipe Tips and Notes sections found in the post, for more tips, options, substitutions, and variations for this recipe! You will also find step-by-step photos there.