Preheat the oven to 350 degrees F. Mix the flour, sugar, baking soda and salt in an 8 x 8-inch, preferably non-stick, baking pan. Make 3 wells in the flour mixture; pour the oil, lemon juice and vanilla separately into them. Pour the water over all and sprinkle in the chocolate chips. Mix well with fork. Bake for 40 minutes, or until toothpick inserted in the centre pulls out clean. Serve warm or at room temperature.
Dust with icing sugar, if desired.