Step 1

To begin the filling, core and dice the apple into 3/8" (1-cm) cubes. Put them in a bowl and sprinkle with the granulated and brown sugar, salt, and water. Mix well and set aside to macerate.

Step 2

To prepare the crisp topping, put the oil in a small pan; if you're using butter, melt it over low heat. Sprinkle with the remaining crisp topping ingredients and stir until crumbly. Toast, stirring often, over medium-low heat for about 5 minutes, or until golden brown. Transfer to a plate to cool.

Step 3

Back to the filling: Sprinkle the cinnamon and cornstarch over the diced apple and mix well. Transfer the apples and all their juice to a microwave-safe ramekin or large mug.

Step 4

Microwave on high for 2 to 3 minutes, or until the apples are soft and the syrup is bubbling. Each microwave oven is different, so keep an eye on it. You can stop the microwave and give it a good stir from time to time (mine takes 3 minutes in my 800-watt microwave).

Step 5

Remove from the microwave and let cool for a couple of minutes before sprinkling with the crumble topping.

Step 6

Serve with a scoop of vegan ice cream (optional).