Heirloom spinach varieties include America, Bloomsdale Long Standing, Bloomsdale Savoy, Monstreux De Viroflay, Merlo Nero, and Giant Thick Leafed.
1 pound fresh spinach, washed, stems removed
3 large eggs
8 ounces ricotta cheese
1 cup whole milk
1/2 cup prepared biscuit mix (such as Bisquick)
1 cup shredded Swiss cheese
1/4 cup onions, finely chopped
1 T. butter
salt and freshly ground pepper to taste
Place spinach in a large pot and add 3 cups water and a dash of salt. Bring to a boil.
Reduce heat to medium-high and cook, stirring occasionally, until spinach is wilted, about 5 minutes. Remove from heat and drain in colander. As spinach cools, use the back of a wooden spoon to press it against the sides of the colander. The spinach must be very well-drained and as dry as possible.
Meanwhile, heat butter in a small skillet and sauteé onions until soft. Remove from heat and let cool.
In a large mixing bowl, combine eggs, ricotta cheese, milk and biscuit mix. Beat until well-combined. Stir in Swiss cheese, onions and spinach; season with salt and pepper.
Spoon mixture into a well-greased 12-cup muffin pan, filling each cup about half-full. Bake in a 325-degree F oven for approximately 45 minutes, until edges are browned and mixture is firmly set.