If you want to add rice noodles to your soup, which I would suggest you do, cook them for 3 minutes in boiling water, drain, and reserve.
Heat a pot over medium heat, add some oil and add the ginger, lemongrass, and curry paste. Cook for about a minute. Tip: Use a cooking rope and attach all the lemongrass together, which makes it easier to remove before serving.
Add the broth, brown sugar, and fish sauce and stir it all together. Now it’s time to add the peppers, don’t cut them, put them whole.
Add mushrooms and about 1/2 the can of coconut milk, stir, and let cook for 5 minutes. Do a taste test, if it’s too spicy for you, add more coconut milk.
Add the shrimps and let it cook for another 4 minutes. Remove lemongrass and whole peppers.
If you opted for noodles, add them to the mix now. Turn heat off.
Add the lime juice, stir and do a final taste test. Adjust with salt as needed. You can garnish with cilantro and thin lime slices for a nice finishing touch.