As you see here, this recipe for aloo tikki is without the stuffing. But, you can definitely make them with the stuffing.  The filling can be you choice. You can fill the patties with boiled chana dal mix, grated paneer or tofu, nuts as well as with nice thick coconut chutney in the centre.  Spicy peas stuffing works great. Make it just like how we make the stuffing for peas paratha or samosa. You can also it with some cheese and chutney mixture within. So, whatever you go with, ensure the stuffing is dry enough. Or the potato mixture will turn out sticky, watery and it won't hold the shape well.