Lightly coat Mason jars with cooking spray. Pour 1 tablespoon heavy cream into each jar. Sprinkle with half the cheese. Carefully pour egg in and cover with remaining cheese and heavy cream. Secure Mason jar with lid. Place jar in a stock pot. Fill up pot with enough water to cover the eggs. Bring water to a simmer over medium-low heat and cook for 8 to 10 minutes or until whites are set. Carefully remove lids and serve with toasted and buttered bread. Garnish with chives.