Bring to a boil; cook for 5 minutes or until potatoes are tender; drain and set aside.
In a large skillet, heat oil on medium-low heat.
Saute onion for 5 minutes.
Add chard and stir 1 minute or until chard is wilted.
Remove from heat and cool slightly.
In a large bowl, beat eggs and egg yolks.
Stir in potatoes, chard mixture, green onion, cheese, milk, salt, and cayenne; spoon about 1/3 cup of mixture into greased regular size muffin cups or spoon 1 generous tablespoon into greased mini muffin cups.
Bake at 375 degrees for 14-16 minutes for regular size muffin cups or 10 minutes for mini muffin cups, or until either is set and slightly puffed.