If your bamboo shoot is whole big pieces then cut them into small pieces and roughly crushed them with a mortar and pestle.
Dry roast cumin, fennel, fenugreek seed, Mustard seed, kalonji till it starts to splutter. Let it cool down.
Now coarsely ground the roasted masala along with bird eye chillies and naga king chillies and chilly powder.
In a mixing bowl add the bamboo shoot, grounded masalas, vinegar and half of mustard oil. Add Salt and mix all together nicely.
Now transfer the mixture in a sterilized jar and pour the remaining mustard oil and close the lid tightly and sunbath it for a week in the sun or for atleast 2-3 days for places with proper sunlight.