In a saucepan, melt the butter with a drizzle of extra virgin olive oil. Add the sliced onions and cook over low heat for 6–8 minutes. Add the flour, stirring well. Once the onions are soft and dry, pour in the hot vegetable broth and continue cooking for another 20 minutes. Meanwhile, evenly toast cubed pieces of bread in a pan with olive oil, salt, and pepper. Set aside. Slice the Pecorino Moliterno Vignaiolo into thin slices and set aside. To serve, season the soup to taste with salt and pepper. Pour it into a bowl with the toasted bread at the bottom. Lay the cheese slices on top so they melt into the warm soup. Garnish with chopped chives.