My favorite fillings are super garlicky kale tossed with tonsof parmesan and pecorino, and (the extra simple filling option) prosciutto and some really good provolone cheese.
One of them is this tried and true recipe for pan-roasted Brussels sprouts, with a tonof lemon juice, and zest, garlic and cumin, plus heaps of grated Pecorino Romano (our favorite cheese that we can't stop snacking on these days).