Prep all the veggies and dice them into small and even pieces. Boil the potato before-hand and cut into cubes. (The reason why you want to boil the potato before hand is because it takes a lot longer to cook and by the time it's fully cooked through everything else will get mushy.)
In a large pan, melt some butter on medium-high heat. Sautee the onions, bell pepper, serranos. Once the onions become transcluscent, add in your carrots and cauliflower. Season with salt.
Now add in your ginger-garlic paste and tomato paste. Combine and cook for a few minutes until the tomato paste begins to caramelize.
Add a little bit of water to help the cauliflower and carrots cook down. Keep an eye on it and make sure nothing over-cooks.
Once the water evaporates, toss in the already boiled potato and then the pav bhaji masala. You can buy it from the store or make your own. I have the recipe fully written under my pav bhaji recipe. If you don't have time to toast and grind everything - just add a little bit of turmeric, cumin, coriander, garam masala, chili powder, and amchur and mix it all together.
Stir in your flour and make sure its well combined to prevent lumps. Then stir in the half and half. And lastly, the peas.
The filling consistency should have some liquid and neither be too thin or thick.
Fill your pie plate with the filling and top with your rolled out pie-crust or puff pastry. Bake at 400 F until crust is golden brown. Serve hot.