Cooking haleem or other dishes specifically on the 9th or 10th of Muharram and considering it an act of worship is not established in Shariah. Moreover, since this practice has become a symbol of certain misguided groups and its observance involves imitating these groups, it should be avoided.
Nevertheless, there are some narrations that mention that increasing one’s expenditure on their household on the 10th of Muharram leads to an increase in their “rizq” (sustenance). Therefore, if someone chooses to spend more on their family on the 10th of Muharram with the intention of obtaining this Fazeelat, there is no harm in doing so.