Dry ingredients: Shift sooji, whole wheat flour, cocoa powder, salt together and keep it aside.
Wet ingredients: In a grinder add oil, and powdered brown sugar, milk, vanilla essence. Grind them until smooth.

Mix dry and wet ingredients together. Keep aside for 30 minutes (covered).
After 30 minutes add baking soda, baking powder and mix it well.
Put batter into a greased baking pan. Sprinkle topping over cake and with help of spatula press topping gently.

Tap the cake pan on a countertop to release any large air bubbles.
Put the cake pan into the preheated pressure cooker and bake it for 1 hour.

Tips :

Grind rava in a mixer for 15 seconds. If using fine sooji no need for grinding.
Adjust sugar according to your taste.
Baking time may vary.
If the batter looks dry after 30 minutes. Add 2-4 tbsp of milk and mix it well.
You can add nuts of your choice.
If baking in Oven: Bake in the preheated oven at 180 deg Celsius or around 360 Fahrenheit for about 1 hour. The baking time may vary. So keep checking the cake after 40 to 45 minutes.

Pressure Cooker Method:

Grease the baking tin with oil and dust it by sprinkling whole wheat flour over greased surface evenly. Pour the mixture into the greased baking tin.

Important Notes:

Use the baking tin of 6 inches in diameter, so that it can easily get into the pressure cooker.
Use a 5-liter pressure cooker. It should be big enough to hold the baking pan.
Baking Tin should be made of Aluminium.

If baking tin comes into direct contact with the base of the pressure cooker, it can burn (overbake) the cake. So use a pressure cooker container which has big holes in it or any aluminum small stand.
No gasket and whistle are needed. Remove them before baking.
Don’t add water to the pressure cooker.

How to Bake In A Pressure Cooker?

Heat the pressure cooker on high heat for 2 minutes. Use sea salt or sand as a layer inside a cooker. Put a steel stand on a layer of salt or sand.
Now put the cake tin containing the cake batter (Do not put water inside the pressure cooker).
Close the pressure cooker lid and do not put the whistle on the lid. Remove the gasket (rubber ring) from the lid.

Lower the flame after 2 minutes. Let it bake for 50 -60 minutes on low flame. After 60 minutes check the cake with a knife, if the mixture does not stick, it means the cake is done.
If batter still sticks to knife then again bake for another 10 minutes. Do not open the lid immediately.
Eggless Pressure Cooker Cake is ready.