Prepare your pie crust (either homemade or premade).
Preheat oven to 425°F.
In the bottom of the crust, sprinkle a small amount of the sugar. Mix remaining sugar and flour together. Then add the currants and water. Pour mixture into the pie crust.
Either cover with a second crust into which vent holes have been made or prepare crumb topping as described below.
For the crumb topping: Mix together flour, sugar and nuts (if using). Cut in butter and oil using two knives to make a crumbly mixture. Sprinkle crumb topping over pie filling.
Bake at 425°F for 10 minutes. Reduce heat to 350°F and continue baking for 25-30 minutes. Enjoy!