Make basil oil (if using – if not, go to step 2).
To maintain the bright green colour of the fresh basil in your basil oil, blanch the basil in boiling water for a minute or two.
Then transfer the basil to food processor and blitz with olive oil. Blitz until the basil is broken down and has formed almost a puree. It doesn’t have to be completely smooth, as you’re going to be draining out the oil anyway.
Allow the basil and olive oil mixture to marinate for 15 minutes or so.
Pour the basil mixture into a chinois over a pot and let mixture drain. We want to allow the mixture to drain for at least half a day or when the oil has completely drained out of the mixture. Once the oil has been drained out, it is ready to be used. Transfer into a squeeze bottle or container.
Combine stock with aromatics.
In a pot (that’s big enough for the soup) over medium heat, combine tomato consommé with lemongrass and ginger. Click here to see how to make your own home-made consommé. If you are making your own consommé, you may want to plan a day ahead. Allow mixture to come to a boil and then switch to low-medium heat. Let lemongrass and ginger simmer and infuse the broth for about 10 minutes.
After the broth has been infused with lemongrass and ginger, give it a taste to ensure the flavour is there. Add baby heirloom tomatoes to the broth and cook for another 10 minutes, until tomatoes are cooked through and begin to shrivel a bit. Leave the lemongrass and ginger in the pot, as the broth will continue to infuse with the flavours.
While the soup is cooking, season the shrimp with 1 or 2 tsp. of salt and sauté in a pan over medium heat with a dollop of olive oil. Sauté until shrimp is pink, edges are browned and meat is cooked through, about 5 minutes. Set aside for garnish.
Get a pot and fill with water. Bring the water to a boil over medium heat. Add vermicelli noodles and boil according to instructions on packet. Be careful not to overcook the noodles – vermicelli generally does not take long and is easy to overcook. Drain and portion out 4 servings into serving bowls or soup bowls.
Add coconut milk and finishing ingredients.
When tomatoes are cooked through, add coconut milk, fish sauce, sugar, rice wine vinegar, and lime juice. Taste as you go with the fish sauce, sugar, and vinegar. Its better to add a small amount at the beginning, taste, and then add more if needed. Adjust according to your taste. Salt to taste. Add thai chilis and stir to combine. Tip: The longer the chilis bathe in your broth, the spicier it will get. Cook for 2-3 more minutes for flavours to combine before serving.
Ladle into bowl with noodles and garnish.
Ladle the soup over vermicelli noodles in the serving bowl. Garnish with cooked shrimp and drizzle of basil oil. Add pepper over shrimp if desired. Congrats! You just made Tom Ka Gai.