First, sift the all-purpose flour/maida with the baking powder and baking soda in a mixing bowl or pan. just keep everything ready as you have to be quick enough to mix the batter.
Grease your cake mould with butter or oil. you can also line the mould with butter paper and then grease the butter paper with oil or butter.
Now take butter and Whisk it in another mixing bowl.
add condensed milk.
add powdered sugar.
after 5 min you will get nice smooth butter texture.There is no need to heat it.
now, slowly add drinking soda and whisk for 2 min.
add dry flour mix and whisk.
add drinking soda and prepare a nice fluffy batter.
Pour the batter in the greased baking mold. shake and tap the sides of the pan so that air bubbles are released.
Preheat the cooker for 5 minutes on high flame with the sand.(We are following the same principle as in the oven but here the sand is heated and the cake gets cooked in the heat produced by the sand.)
Now, keep the flame in low and place the Mould with the cake batter carefully inside the cooker.
Close the cooker, and Relax as it will take 4o minutes to 1 hours for the cake to be done.
Check it after 40 minutes by inserting a wooden toothpick in the center of the cake, if it comes out clean, your cake is done, otherwise cook for some more time. (Mine took 45 min)