elt the butter and olive oil in a medium skillet over medium heat, add the onions and cook for about 10 to 12 minutes or until golden brown, stirring occasionally.reheat the oven to 375 F.lace all the ingredients in a medium bowl and mix well.ivide mixture equally into greased ramekins or individual oven proof dishes and bake for about 20 minutes or until tops are puffed and set.erve warm.