Preheat oven to 375 degrees.
1. Cut butter into 1-inch pieces and place in the bowl of an electric mixer fitted with the paddle attachment. Mix on medium speed until smooth and lightened in color, about 1 minute. Stop the machine and add the cream cheese mixture, and mix on medium speed for 1 minute. Add the superfine sugar in a steady stream, then blend in the eggs, the reserved yolk, and the vanilla. Reduce the mixer to low speed and add flour mixture in 3 additions, mixing just until blended after each addition.
2.Scoop muffins into a prepared muffin pan.
Bake for 22-25 minutes, or until the muffins are golden brown an the tops are springy to the touch. To ensure even baking, toward the end of baking time, rotate the pans top to bottom and front to back. Remove from the oven. Drizzle the glaze over the muffins while they are slightly warm or dip tops of muffins into glaze. Allow the glaze to set before serving. Store in an airtight container.
To prepare Orange Glaze
3. Combine sugar, orange juice, orange zest and corn syrup. Whisk until smooth and pour over muffins.