Stir the milk and vinegar together, allow to stand approximately 10 minutes, until curdled
Preheat oven to 400°F. Grease a Dutch oven with butter, then place in oven to preheat
In a bowl, mix the flour, sugar, baking soda, and salt. Gradually pour the milk and vinegar mixture into the dry ingredients, stirring until the dough just comes together
Turn dough onto a floured surface, knead lightly, and shape into a round. Place in a preheated Dutch oven, cut an “X” on top, cover, and bake until golden