Peel the shrimp and remove the heads, then add all the shells, tails and heads into a stainless steel pot (or Instant Pot) with vegetable oil. Saute over medium high heat, pressing out any tomalley from the shrimp heads with your spatula.

Once the bits that are stuck to the bottom of the pot start to brown and smell like grilled shrimp, deglaze with water and scrape all the bits off the bottom of the pot.

Simmer over medium low heat for 45 minutes.

If using an Instant Pot, use the soup function and turn the seal to "venting" when the timer is done.

Strain, making sure to get out any liquid from inside the shrimp heads. You need about 4 cups for the soup, but if you don't have enough you can add water.

Add the shrimp or chicken stock, lemongrass, makrut lime leaves, galangal and chillies to the pot. Bring to a boil and let it boil for about 5 minutes until you can smell the fragrance of the herbs from the pot.

Add button mushrooms, cheese tofu and corn (if using) and bring back to a boil.

Add the fish sauce, chilli paste, sugar and stir. Taste and adjust the seasoning to your liking. (You may need to add more chillies, or sugar depending on how sweet your chilli paste is).

Add the shrimp and when the soup starts to bubble again, turn off the heat. Let the residual heat of the soup cook the shrimp completely for another minute or so.

Add the lime juice and adjust seasonings according to your liking.

Garnish with cilantro leaves and serve with rice. It's fine to eat it on its own too!