Preheat the oven to 350°. Grease and flour a 9-inch loaf pan. In a large heavy saucepan over medium heat, begin melting the butter, stirring occasionally. When it's half melted, remove the pan from the heat and stir until fully melted. Stir in the sugar, vanilla, salt, sour cream and egg.
Add the baking soda and baking powder in pinches, breaking up any lumps with your fingers. Stir thoroughly. Stir in the flour, just until blended, then the chocolate chips. Pour and scrape the batter into the pan and bake in the preheated oven for 45 to 50 minutes, or until a tester inserted in the middle comes out with just a crumb clinging to it.
Cool on a rack for 10 minutes. Remove from the pan and cool on the rack for about 15 minutes more.