Preheat the oven to 375°F (190°C).
Mix flour, baking powder, sugar, and salt in a medium bowl.
Pour melted butter, add yogurt or buttermilk and quickly mix with a spoon or spatula. It needs to be incorporated, but not overmixed.
Drop 9 mounds onto the peach filling, making three rows of 3. Leave space between them and around the edges so that the fruit juices can bubble up when baked.
Bake for about 35 minutes and check to see if the biscuits are fully baked. They will be golden and dry but lift one of them with a fork and check that there's no unbaked dough. Sometimes they look perfect, and the juices are bubbling, but there's still some raw dough.
If this is the case, bake it for 5-10 more minutes or until it's fully baked when you lift it a bit. You might want to loosely cover the surface with a piece of aluminum foil to prevent the biscuit topping from darkening too much while it continues baking.
Let cool on a wire rack until warm enough to serve.
Serve with ice cream or whipped cream if you feel like it.
Refrigerate leftovers, covered. Warm slightly in a medium oven before serving them again.