Preheat oven to 375 degrees.
Place butter in a 13 x 9 inch baking dish and melt in the oven.
While the butter's melting, whisk the flour, 1 cup sugar, baking powder and salt together in a medium bowl.
Gradually add half and half while continuing to whisk until smooth. Set aside.
In a separate bowl, toss peaches, brown sugar, remaining granulated sugar, cinnamon, nutmeg and vanilla until combined.
Remove baking dish from oven and pour batter over the butter. Don't stir.
Pour peaches over the batter and spread with a spatula.
Bake for 40 minutes or until crust is golden brown. Allow the cobbler to rest for 10 minutes before serving.
Top with vanilla ice cream or whipped cream, if desired.