To prep the banana blossom, rinse it well, and begin removing each layer of leaves, collecting the small blossoms within as you separate the leaves. Discard the tougher, outer layers, and continue removing leaves, retaining the tender inner leaves and small blossoms.
Stack about five tender banana leaves at a time and cut the stack crosswise into long thin strips. Fill a large bowl with water and a big squeeze of lemon. Drop the squeezed lemon half into the bowl. Place the strips in the lemon water. For very tiny blossoms, simply pinch off and discard the tips.
When all the small blossoms are cleaned, chop them and add to the lemon water. Add about two tablespoons of salt and massage the leaves and blossoms under the water, pressing them between your fingers for a few minutes. This process removes bitterness, and the water should become discoloured. Drain off the water, then fill the bowl with fresh water, lemon juice, and salt. Repeat, massaging and pressing under the water for a few minutes more. Drain off the water and pat the leaves and blossoms dry. This unique ingredient is now ready to be cooked.
Heat a sauté pan over medium-high heat. Add the oil to evenly cover the bottom, then add the shallots and stir for two to three minutes until they're translucent. Add the garlic, ginger, chilli, and prepped banana blossom. Shake the pan to spread evenly and sauté until the blossom takes on a bit of colour and softens, (four to five minutes), stirring to avoid burning the garlic.
Lower the heat to medium and stir in the coconut milk, tamari, and half a teaspoon of salt. Continue stirring until the coconut milk reduces slightly in volume (stirring helps keep the coconut milk from separating). Remove from the heat and squeeze in the juice from one lime half. Taste and add more tamari, salt, and/or lime juice as needed.
To assemble, divide the noodles among two to four noodle bowls. Ladle in the coconut banana blossom mixture, and add the cucumber, lettuce, coriander, green onions, sliced chilli (if using), and lime wedges for squeezing.