Heat the oven to 400°F / 200°C. Slice 1/4 inch off the top of the garlic head to expose the cloves. Drizzle with 1 teaspoon oil and a pinch of salt. Wrap loosely in foil.
Roast 35 to 40 minutes until the cloves are soft and deep gold. Cool 5 minutes, then squeeze the cloves from their skins into a small bowl. Mash lightly with a fork.
Air fryer option: 375°F / 190°C for 25 to 30 minutes, checking at 20 minutes.
Soak and simmer the base
Soak the cashews in 1/4 cup hot water for 15 minutes while the garlic roasts.
Heat 1 tablespoon oil and 1 tablespoon butter in the pan over medium heat. Add sliced onion if using. Cook 4 to 5 minutes until soft and lightly gold.
Add grated ginger. Stir 30 seconds.
Add tomatoes, turmeric, Kashmiri chilli, coriander, cumin, and a pinch of salt. Cook 6 to 8 minutes until the tomatoes break down and the oil starts to separate at the edges.
Add 1/2 cup water. Simmer 3 to 4 minutes. Cool 5 minutes.
Blend
Blend the tomato mixture with the soaked cashews (and their water) and the roasted garlic until completely smooth. Scrape the sides once. The paste should look silky, not grainy.
Finish the makhani
Wipe the pan if needed. Melt 1 tablespoon butter over medium-low heat. Pour in the blended gravy.
Add 1/2 cup warm water. Simmer 5 to 7 minutes, stirring, until the gravy thickens enough to coat a spoon. Add more water if it is too tight. Taste for salt and add sugar if the tomatoes taste sharp.
Stir in cream, crushed kasuri methi, and garam masala. Simmer 1 minute on low. Do not boil hard after the cream goes in.
Add paneer cubes. Warm gently 2 to 3 minutes so the paneer softens in the gravy. Turn off the heat. Swirl a teaspoon of butter or cream on top.
Garnish with cream, cilantro if you like, and a pinch of kasuri methi. Serve hot with naan, roti, or jeera rice.
Notes
Roast until the cloves squeeze out easily and look caramel-gold. Pale cloves still taste raw in the blender.Soak cashews in hot water so the gravy blends smooth. Cold water needs a longer soak.Onion is optional. Skip it for a cleaner tomato-garlic makhani, or keep it for a slightly thicker body.Do not fry the paneer hard unless you like chewy edges. Warming it in the gravy keeps it soft.For a vegan version, use firm tofu instead of paneer and coconut cream or cashew cream instead of dairy cream and butter (use oil for the early steps).Gravy keeps in the fridge 3 to 4 days. Freeze the gravy without paneer for up to 1 month. Add fresh paneer when reheating.Leftover roasted garlic: mash into butter for toast, or stir into dal.