I read about panch phoron on a cooking blog. The writer of that blog was so enthusiastic about the spice mix and how it revolutionizes vegetable dishes, I decided I wanted to give it a try. And indeed, the results of spicing up your vegetable dishes with panch phoron are very good.
I made my spice mix like sneff describes above: equal amounts of fennel, black mustard, fenugreek, cumin and nigella, mixed together. Using that mix, I've decided that it could use a bit less of the nigella seeds. Nigella has a slightly metallic taste that I find a bit overpowering. So I recommend halving the amount of nigella seeds.
A very simple dish to make with panch phoron: spiced spinach. For two people, use 400 grams of spinach (either fresh or frozen, but not the kind with cream!). I usually cut fresh spinach into smaller pieces because that keeps it from turning into spinach spaghetti after cooking and makes it easier to eat. But you don't need to do that. Either way, wash your fresh spinach well. Frozen can just be used as is, don't defrost. (I use spinach frozen into small blocks, I recommend those for this recipe. It's hard to stir fry a brick of spinach).
Chop up two cloves of garlic and grate an equal amount of fresh ginger. Optionally, also cut a chili pepper into small bits. Heat up some vegetable oil in a wok or similar. Add a good teaspoon of panch phoron and fry this until the seeds begin to pop. Then add the garlic and ginger (and chili if you use it) and stir around a bit. Then add your spinach. Turn down the heat a bit and keep stirring until wilted if you use fresh spinach, for frozen stir around once in a while and let defrost. When the spinach is done, add some salt to taste and there it is. Serve with rice. Nice as a side dish for a creamy curry, or add some chickpeas or lentils and eat as a vegetarian main dish.