Preheat oven to 200 degrees C. Grease a 2 litre baking dish with margarine.
In a medium saucepan, combine sugar, cornflour, water and strawberries. Cook over medium heat, stirring constantly, until thick and hot. Pour mixture into the prepared baking dish. Dot with 2 tablespoons margarine.
In a bowl, combine flour, 1/4 cup brown sugar, baking powder and salt. Blend in the 3 tablespoons butter. Stir in cream. Mixture should be soft. When you spoon dough onto the berries, it will probably sink to the bottom. Just try to spread as well as you can. Don't worry, it comes out good.
Bake for about 20 to 25 minutes in the preheated oven. When the cobbler is almost done, mix the 1/4 cup margarine and 1/4 cup brown sugar and heat them in a saucepan or in the microwave (whichever is easier for you). When the topping is heated, brush it on the top of the cobbler and bake for another 5 to 10 minutes.