Prepare the filling: Combine apples, mulling spices, vanilla, flour and salt in a large bowl. Stir well to combine. Place in baking dish. Add water, and top with butter pieces.
Prepare topping: In a large bowl, mix all topping ingredients together. Stir until just combined.
Drop batter by the spoonful over the apple mixture. Topping will spread to cover as it bakes.
Bake 35-to-40 minutes, until topping is golden brown.
Cool slightly and serve with vanilla ice cream or fresh whipped cream.
