Combine 3 tablespoons bread crumbs, kosher salt, black pepper, cayenne, rosemary, garlic, milk, and Worcestershire sauce in a bowl. Mix to create a slurry. Let sit for 15 minutes to hydrate bread crumbs.
Mix ground lamb and ground beef together gently in another bowl using 2 forks. Mix in bread crumb slurry using the same 2-fork method until just combined. Wrap in plastic wrap and refrigerate for 1 hour.
Place flour, eggs, and bread crumbs in 3 separate shallow dishes. Portion out nuggets using a 1 1/2-tablespoon scoop. Roll nuggets in flour; shake off excess. Dip into beaten eggs using your free hand, shaking off excess between fingers. Transfer to bread crumbs and coat with your dry hand, pressing gently to make sure surface is covered. Sprinkle leftover bread crumbs over a plate and add the nuggets. Refrigerate, uncovered, for 1 hour.
Meanwhile, combine mayonnaise, mustard, ketchup, and chipotle powder in a bowl for sauce. Refrigerate until ready to use.
Heat oil in a deep-fryer or large saucepan to 375 degrees F (190 degrees C).
Fry nuggets in the hot oil until golden, 3 to 4 minutes. Transfer to a paper towel-lined plate and let rest and finish cooking for 3 to 4 minutes before serving with sauce.
Nutrition FactsCalories: 252% Daily Value *Total Fat: 22 %Saturated Fat:Cholesterol: 23 %Sodium: 23 %Potassium: 5 %Carbohydrates: 7 %Fiber: 3 %Sugar:Protein: 24 %Exchange Other Carbs:Vitamin A Iu:Niacin Equivalents:Vitamin B6:Vitamin C:Folate:Calcium:Iron:Magnesium:Thiamin: