Using kitchen scissors or a knife, remove the leaves from the stems of the chard. Discard the stems. Chop
the leaves into 1-inch pieces. In a large nonstick skillet, heat the oil over medium-high heat. Add the onion and cook until soft, about 5 to 7 minutes. Add the garlic and cook for 1 minute longer. Add the chard and cook, stirring constantly, until wilted, about 2 minutes. Allow the mixture to cool slightly. Place the ricotta cheese, peas
, mozzarella cheese
, Parmesan cheese
, basil, salt, and pepper in the bowl of a food processor
. Add the cooled chard mixture and blend until smooth. Spoon the mixture into the prepared pastry bag
and fill each manicotti shell with the filling. Place the stuffed manicotti in the prepared baking dish.