Wash your eggplant, slice into 1 to 1.5 inch disks, then wash again, and drain well.
Season the eggplant with turmeric, red chili, and salt. Make sure to cover all the pieces and gently massage the seasoning into the disks to form a light paste
Heat your pan on high, pour in your oil and let it heat up. Then fry your eggplants for 2-3 minutes, flipping halfway through until both sides are nice and golden brown with a bit of char. Take them out of the pan and onto a plate once done. Be gently so they don't break.
In a new pan, saute your onions on medium/medium-high till they start to brown, you can use the oil from frying the eggplants if you want.
Then add in your bay leaf, dry red chilis, and panch phoron (bengali five spice). Fry for a couple minutes until the cumin and mustard seeds start to pop (make sure the chili/onions don't burn), and all the whole spices are fragrant.
Add in your ginger garlic paste, and fry for a few minutes until the raw smells are gone, adding splashes of water to keep it from burning if needed.
Then add in your powdered spices and salt (red chili, turmeric, and gorom mosholla/garam masala). Fry for a couple minutes, do not burn.
Then add in a 1/4 cup of water, reduce until the oils come out, fry in the oil for a minute and then pour in more water and repeat this step 3-4 times. The longer you go the better your curry will taste.
Then add in your tamarind paste, sugar, and some water. You can mix everything together with a 1/4 cup of water to adjust the flavors to your liking first as it will be harder to gauge the flavors once you add it into the aromatic curry.
Let the mixture boil for a few minutes to come together. Then add about a cup of water, stir and bring back up to a simmer, then turn your heat down to medium-low.
Gently slide in your fried eggplant, and swirl the pan around to cover them in the gravy.
Let the dish simmer on medium low until you get to the consistency you want, gently flipping the eggplants halfway through. The sauce will thicken more as it sits so reduce accordingly.
Taste and adjust salt/sugar if needed. Take it off the heat, and serve warm.