Now, in a small bowl, dissolve instant coffee powder in hot water. Set it aside and let it cool down.

In a large bowl, combine khapli atta, salt, and baking powder. Whisk it well and keep it aside. For the cake batter, in another large bowl, beat unsalted butter and powdered sugar together until fluffy and a pale, light colour.

Now, in the cake mixer, slowly add the beaten eggs, one at a time, and set the mixer on a low speed. If they start to curdle or split, add a spoonful of dry flour mix. Keep on adding the eggs and a bit of flour, if necessary, until all the eggs are added. Then, keep the mixer on slow speed, add the coffee mixture, milk, vanilla extract, and the rest of the flour. Wait until the mixture is well combined, and lastly, fold in the chopped walnuts, if using.

Transfer the cake mixture into the greased and lined loaf tin, then bake for 1 hour. To check if it is cooked, take a toothpick test. Insert it in the centre; if it comes out clean, it is ready.