Bring water to a boil in a large Dutch oven; add spinach, and cook 1 minute or until the spinach wilts. Drain well. Place spinach on paper towels, and squeeze until barely moist. Place spinach, milk, and pear quarters in food processor, and process until smooth.
Melt margarine in the Dutch oven over medium-high heat. Add spinach mixture, and cook 5 minutes or until liquid evaporates. Remove from heat; stir in salt and nutmeg. Garnish with the pear slices, if desired.