In a mixing bowl, combine the milk, butter, egg, cheddar cheese, cream cheese, and Sriracha sauce. Mix thoroughly.
Place the penne pasta in a casserole or baking dish, then pour the cheese and Sriracha mix over top. Lightly stir to allow the mix to cover all areas of pasta.
Sprinkle the panko bread crumbs atop the mac and cheese. Sprinkle the remaining cheddar cheese (optional) on top of the bread crumbs.
Cook the mac and cheese for approximately 45 minutes, then remove from heat. Sprinkle with Sriracha powder, then serve.