Add cornflour, salt, black pepper powder, red chilli powder, garam masala and coriander powder to a bowl. Add water as per need to make a slurry.
Now cut paneer into small cubes and collect them in a bowl. Add lemon juice and toss the paneer cubes well in it.
Now dip each paneer cube in the corn flour slurry and coat in breadcrumbs. Meanwhile, add mustard oil to a pan and heat till smoke emerges. Now gently drop the coated paneer cubes in the hot oil and fry from both sides until golden in colour. Fry all the paneer cubes in small batches.
Once all the paneer cubes are fried, serve them with tomato ketchup and mint chutney.