Preheat oven to 375°F. Butter a 9x13 baking dish. Bring a large pot of salted water to boil.
Cook pasta in boiling water until al dente (2 minutes less than package directions). Drain and set aside in a mixing bowl.
In the same pot, melt 4 tablespoons butter over medium heat. Whisk in flour and cook for 2 minutes, stirring constantly with whisk.
Gradually add warm milk and cream, whisking constantly to prevent lumps. Bring to a simmer and cook for 5 minutes until thickened.
Remove from heat. Add cheddar, gruyere, and fontina cheese, stirring until completely melted and smooth.
Stir in Dijon mustard, garlic powder, cayenne, salt, and pepper. Taste and adjust seasoning.
In a small pan, melt 2 tablespoons butter. Add lobster meat and lemon juice, tossing gently for 2 minutes just to warm through. Remove from heat.
Pour cheese sauce over cooked pasta in mixing bowl. Gently fold in lobster meat. Transfer to prepared baking dish.
In a small mixing bowl, combine panko, melted butter, parsley, and parmesan. Sprinkle evenly over mac and cheese.
Bake for 25-30 minutes until bubbly and golden brown on top. Let rest 5 minutes on cutting board before serving.