Jalan Sawangan, a short street just south of the alun-alun, is the unofficial centre of Purwokerto's mendoan culture. Half a dozen tented warungs set up every afternoon to fry sheets of fresh tempeh in a thin batter of rice flour, coriander and turmeric — the trick is to pull the tempeh out of the oil while it is still slightly soft and pale, hence the name (mendo means "half-cooked" in Banyumas Javanese). They are served piping hot with sambal kecap (sweet soy sauce with sliced bird's-eye chilli) and a plate of plain rice.
The most established stall is Warung Mendoan Pak Naryo, on the south end of the street, but the others are nearly indistinguishable in quality — pick whichever has the longest queue. A plate of mendoan with rice will cost under 20,000 rupiah and is the cheapest decent meal in the city. The stalls open from around 3pm and stay busy until the tempeh runs out, usually by 9 or 10pm.