Heat 3 cups of chicken stock in a stock pot over medium heat.
With the side of your knife smash the bulb ends of the lemon grass. Trim the top ends off and chop each stalk in half. (See Note 1). Trim the stem off the jalapeño and slice lengthwise down the middle. Add to the simmering stock for 15 minutes. Remove and discard.
Next add the coconut milk, chunky peanut butter, Sambal Oelek Chili Paste and fish sauce. Stir to incorporate.
Crack the crab legs open and remove the crab meat. Do a quick chop for bite size pieces and set aside.
Wash the shrimp that was already cleaned and deveined. Add the seafood and water chestnuts to the pot and cook on low for another 5 minutes until heated through and serve topped with basil.
Feel free to substitute 1 tablespoon lemon grass paste if fresh lemon grass is not available.
Please note that fish sauce does have a high sodium content for those watching their intake, but the nuanced flavor is amazing.