"Add the curry paste according to how flavorful/spicy you want the sauce. Brands differ in heat - I often use the Thai Kitchen brand because I can easily find it in my grocery store and I use the full 4 tablespoons but I don't mind a touch of spiciness. It's really important to use natural unsweetened peanut butter here. I've tried it using your every day creamy peanut butter (like Skippy or Jif) and the texture and flavor is overly sweet and just weird. You really want that natural peanut flavor to come through.The recipe says to simmer the ingredients and that definitely deepens the flavor and thickens the sauce but as I mentioned in the post above, several times, I've skipped the stove step and just blended everything up and it's tasty, tasty...."