First soak all the ingredients under the "Vindaloo paste" category above and keep it aside, covered, for atleast 20 mins
Next, wipe the mushrooms nicely with a lightly damp tissue paper or thin dry cloth. You will see that while wiping the top-most layer starts peeling off.
Cut the mushrooms into medium size pieces and marinate with a pinch of salt and 1 tbsp vinegar for about 10 minutes. Keep it aside, uncovered.
Add just enough water to to this mix and grind into a smooth paste
Heat coconut oil in a pan and add onions. Add little salt and cook till they turn golden brown in medium flame.
Now add the ground paste and fry for 10 minutes in low flame or till the raw smell goes. You may add a little water in between if it starts to stick to the pan.
Add the mushrooms along with 3/4 cup water and mix well. Cover and cook in low flame for about 15 minutes. Check if the mushrooms have cooked.
Now add the chopped tomatoes, cover the pan and cook in low flame till it's almost mushy.
Add 1/2 tsp pepper and salt if required. You can stop when you reach the required consistency.