Preheat the oven to 375 degrees F (190 degrees C). Grease a muffin tin, or line with paper liners.
In a medium bowl, cream together the butter and sugar until light and fluffy. Beat in the egg and vanilla, then gradually stir in the milk and yogurt. Add the flour, and mix until just blended. Fold in the white chocolate chips and sprinkles. Spoon into 6 muffin cups.
Bake for 15 to 20 minutes in the preheated oven, or until the tops spring back when lightly touched. Cool muffins before removing from the tin.
