In a large skillet over medium heat saute the onion in the oil and butter, avoid browning the onions. When onions become translucent, add the garlic and the rice and stir for a couple of minutes. Add the white wine and stir until wine is absorbed. Add a ladle of broth, stirring continuously until broth is almost completely absorbed. Repeat until rice is tender and the mixture is creamy. In another skillet on high heat pour in 1/4 cup of the olive oil and sear the scallops on both sides for about 1 minute and set aside. Then saute the vegetables in the remaining 1/4 cup of olive oil until tender. Add the vegetables to the risotto and stir in the cheese, butter and lemon juice. Season the risotto mixture with the salt and pepper. Divide the risotto between 6 plates and place 4 scallops right on top.