Combine cream cheese with egg yolk, baking powder, and a dash of salt; mix until blended and smoothe. Cut 4 small rounds from each slice of bread using a biscuit cutter or small glass. Spread each round lightly with mayonnaise. Spread each with a thin layer of deviled ham. Spoon the cheese mixture on the ham. Sprinkle with paprika. This much can be done ahead and the appetizers frozen, if you desire. To serve, put into a moderately hot oven(375) for 12-15 minutes, or until puffed and browned. Serve immediately. Makes 45 appetizers.