Pre heat oven at 170 deg C for 10 to 15 minutes to begin with.
Take a square baking tray firstly. I used 8 Inch tin. Grease with butter all the sides and base.
I lined with butter paper/ baking sheet. You can also dust with flour instead.
After that, take flour, baking soda, baking powder, salt in a sieve. Sift to ensure even mixing. Set aside.
In another mixing bowl, take soft butter and beat for 30 seconds. I used my hand mixer, but you can do in stand mixer as well as hand whisk.
After that, add sugar and beat until mixed well.
Furthermore, pour milk, vanilla and curd. Beat well until mixed properly.
Now, add the sifted dry ingredients little at a time. I did in three parts.
Gently fold in to the wet ingredients. Do it patiently, do not over mix.
Repeat to finish all. The batter should be smooth without lumps.
Furthermore, transfer the batter to the lined baking tin.
Spread evenly and tap twice to ensure there is not large air bubble.
Bake for 20 minutes. Keep an eye after 15 minutes and check by inserting a tooth pick. If it comes out clean, then take out from oven.
Invert over a wire rack for cooling. Peel off the baking sheet after 15 minutes.
Let it completely cool down. Store in refrigerator atleast 2 hours or overnight.
After that, take out and trim the sides. Then cut into squares.