Preheat oven to 375°F. Lightly butter six custard cups. In a saucepan, heat spinach and onion to wilt for 2-3 minutes or until warm, using only the water that clings to the leaves of the spinach. Remove from pan, drain spinach mixture, squeeze out excess liquid and chop finely. Transfer to a bowl. Beat in butter and cheese until melted, using a microwave if necessary. Stir in ½ cup cream and salt and pepper. Pour mixture evenly into prepared custard cups. In the center of each cup, make a small well and break an egg into each well. Spoon remaining cream over eggs. Place custard cups in a roasting pan and pour enough water to come two-thirds up the sides of the cups. Bake 20-30 minutes or until eggs feel firm to the touch.
While eggs are baking, make Parmesan bowls. Heat a nonstick skillet over medium-high heat. Sprinkle Parmesan cheese into a disk shape, keeping cheese light around the edges to look lacy. When the cheese is slightly golden underneath, carefully remove it using a spatula and use your fingers to shape the cheese around a cold glass custard cup. Repeat 6 times to make 6 Parmesan bowls.
Gently remove eggs from custard cups and slide into Parmesan bowls. Garnish with sliced almonds and an orange slice.