Position the rack in the center of the oven & preheat to 375°F Spray the cups and the rims with the nonstick spray, or drop in the paper cups. If using a silicone pan, spray as directed, then put on a cookie sheet.
Whisk the flour, baking powder,and salt in a medium bowl until well blended. Set aside.
Place 4 ounces of the white chocolate and all the butter in the top of a double boiler set over simmering water. If you don't have a double boiler, place the chocolate and the butter in a heat safe bowl that fits snugly over a small pot of simmering water. Stir constantly until half the chocolate and butter is melted. Remove from the pot, then continue stirring, away from the heat, until the mixture is smooth. Cool for 10 minutes.
In a large bowl, whisk the egg and sugar until thick and pale yellow, about 2 minutes. Whisk in the cooled chocolate mixture until smooth, then whisk in the milk, orange extract, and vanilla extract.
Use a wooden spoon to stir in the remaining chopped white chocolate or white chocolate chips. Stir in the prepared flour mixture, just until moistened.
Fill the prepared tins 3/4 full. Use any leftover batter for a second baking. Bake for 20 minutes, or until the muffins are browned with slightly rounded tops, and a toothpick inserted into the center of one comes out with a crumb or two attached.
Set the pan on a wire rack to cool for 10 minutes. Gently rock each muffin back and forth to release it from the pan. Then set them on the wire rack for an additional 5 minutes before serving. If storing these muffins, cool completely before storing in airtight containers or freezer safe bags. The muffins will stay fresh for up to 24 hours at room temperature, or for up to 2 months in the freezer.