2) Place one tablespoon of the ricotta filling in the centre of a wonton wrapper. Brush the edge of the wrapper lightly with water. Fold the wrapper in half, enclosing the filling completely and forming a triangle. Pinch the edges to seal. Transfer the ravioli to a baking sheet. Repeat with the remaining filling and wrappers.
3) Working in batches, cook the ravioli in a large saucepan of boiling salted water until just tender, stirring occasionally, about four minutes per batch. Transfer the cooked ravioli to a large shallow bowl.
4) Melt the butter in a heavy small frying pan over a medium heat. Add the oregano and stir for one minute. Season, to taste, with salt and pepper. Remove from the heat and pour over the ravioli. Toss gently to coat; sprinkle the pecorino over the ravioli and serve.