Preheat oven to 375 F. Lightly oil a 9 inch baking dish (or spray with non-stick coating).
In a large pot of salted water, cook pasta according to package directions. Add cauliflower florets to the pot for the last 3 min. of cooking. Rinse and drain well.
While the pasta is cooking, finely chop parsley, tarragon, cilantro, basil and shallot and add to a large mixing bowl. Add garlic, lime, Dijon mustard, sour cream, milk, cheeses and mix thoroughly. Add cooked pasta and cauliflower and mix well. Add salt and pepper to taste and additional milk if needed to reach desired consistency.
Spread pasta mixture in the prepared baking dish and place in the oven. Cook until bubbly and browned, approx. 12-15 min.
While pasta is cooking in oven, heat olive oil in a small fry pan over medium-high heat. Add Panko crumbs and cook, stirring frequently, until browned and toasted. (approx. 2-3 min.) Remove from pan and set aside.
Remove pasta from oven and garnish with Panko crumbs. Serve immediately.