About Xaak: Xaak is the Assamese word for cooked greens — a category, not a single dish. In Assamese homes, some form of xaak is on the table every single day. The technique is minimalist on purpose — whatever greens are available, washed and stir-fried in mustard oil with a few aromatics, the dish is meant to taste of the greens, not the masala. This recipe uses a typical winter combination but you can adapt it season by season.
Choose your greens: Use a generous 3 cups of mixed greens (about 250g). Traditional Assamese mix includes — mustard leaves (lai xaak), spinach (palong), dhekia fern (in season), khutura (amaranth) and sometimes radish leaves or watercress. Use whatever is freshest at your market.
Wash exhaustively: Greens often look clean but hide grit between leaves and at the base of stems. Plunge into a large bowl of cold water. Swish around vigorously for 30 seconds. Lift out into a colander — never tip the bowl as that pours dirt back over the greens. Repeat with completely fresh water 2 more times.
Dry well: Spread the washed greens on a clean kitchen towel. Pat dry, or use a salad spinner. Wet greens will steam rather than stir-fry, releasing too much water and turning the dish into a soup.
Trim stems: Examine each stem. Tender thin stems (spinach, amaranth) can stay. Thick fibrous central ribs (mustard leaves, kale) should be removed — fold the leaf in half and run a knife along the spine.
Rough chop: Stack a few leaves, roll into a log, slice into 2cm wide ribbons. Keep the leaves and any tender stems separate from any thicker stems — the thicker stems need a head start.
Prep the aromatics: Slice 3 garlic cloves into thin slivers — slivers fry up beautifully and crisp at the edges. Take 2 dried red chillies — break each in half, shaking out most of the seeds.
Measure mustard oil: Use 1 tbsp pure mustard oil. Mustard oil is essential here — its pungent character is the soul of Assamese xaak. Refined or neutral oils do not work. If you cannot get mustard oil, use cold-pressed sesame as a less-than-ideal substitute.
Heat the oil correctly: Heat a wide kadai or wok on medium-high heat. Pour in the mustard oil. Heat until it just begins to smoke and turns from yellow-orange to a paler shade — this removes the raw pungency and brings out the warm aromatic side. About 1 minute.
Fry red chillies: Reduce heat to medium. Add the broken dried red chillies. Fry 20 seconds until they puff up slightly and turn a darker red — be careful not to burn them.
Fry garlic: Add the slivered garlic. Fry for 30 to 45 seconds, stirring constantly, until just turning golden. Garlic moves from raw to golden to burnt in seconds — stay attentive.
Add thicker stems first: If you separated thicker stems, add them now. Stir-fry 1 minute on high heat to give them a head start — they need longer than leaves.
Add the greens: Tip in all the leafy greens. They will look like an impossible mountain of greenery in the pan — do not worry, they reduce dramatically. Stir to coat with the spiced oil.
Add turmeric: Sprinkle 1/2 tsp turmeric powder over the greens. Stir quickly to distribute. Turmeric burns on direct contact with hot oil so let it touch the greens immediately.
High-heat stir-fry: Cook on high heat for 3 to 4 minutes, tossing every 20 seconds. The greens will collapse, release some water, and that water should evaporate. The end result should be wilted, glossy and still vibrantly green — never dull or greyish.
Season: Add salt to taste — about 1/2 tsp. Stir through. Taste a leaf — it should be tender, glossy with mustard oil, and have a clean fresh flavour with the gentle warmth of garlic and chilli behind it.
Optional finishing: Some Assamese cooks add a final 1/2 tsp raw mustard oil off the heat for an extra punch, or a tiny squeeze of lemon for brightness. Both are excellent.
Serve immediately: Xaak is best served the moment it is made. Pile onto a serving plate. It is the daily side that accompanies rice and dal in every Assamese meal — simple, fresh, deeply nourishing.
Seasonal variation: This same technique works for spring dhekia ferns (par-boil them first 5 minutes), summer tender amaranth, and even fenugreek leaves in winter. Adjust greens; technique stays.