Break the pasta noodles in half. Cook in salted water according to package instructions until it is just below al dente (it should not be completely crunchy but should still be too chewy to eat; the pasta will cook more in the oven). Drain and set aside.

Place the sun-dried tomatoes in a small bowl and cover with hot water. Set aside to rehydrate (if using oil-packed sun-dried tomatoes, you can skip this step; simply drain them and pat off excess oil).

In a Dutch oven or similar large, deep pot, heat the butter over medium heat. Add the onion and sauté until softened, about 5 minutes; adjust the heat as needed so that the onion cooks but does not brown.

Add the mushrooms then increase to medium-high heat. Sauté until the mushrooms begin to soften and give up their liquid, about 5 minutes.

Stir in the garlic and vinegar and let cook 30 seconds.

Sprinkle the flour over the top, then stir to coat. Continue cooking and stirring periodically for 2 minutes. No white bits of white flour should remain.

Slowly pour in 3 cups of the broth, stirring all the while to avoid any lumps. Bring to a gentle boil and let cook, stirring often to prevent sticking to the bottom of the pot, until the mixture is reduced by about one-third, 6 to 8 minutes.

Remove the pan from the heat. Add the diced cream cheese, Worcestershire, smoked paprika, salt, and pepper. Stir until the cream cheese is mostly melted (a few bits may remain, which is fine).

Stir in the sun-dried tomatoes, chicken, vegetables, Provolone cheese, and Parmesan cheese, until the cheese is melted. Then stir in the Greek yogurt. Taste and add additional salt and pepper as desired.

Add the cooked spaghetti and stir it to combine. If it looks super thick, add more of the remaining 1 cup broth as needed. It should look a little bit soupy, as some of the liquid will cook off in the oven.

Transfer the pasta mixture into the prepared baking dish. Sprinkle the Panko over the top. Bake for 25 minutes, or until the tetrazzini is hot and bubbly. If you’d like to brown the topping further, place under the broiler for 1 to 2 minutes, watching carefully so that it does not burn. Remove from the oven and let rest a few minutes before serving.