Well, you could make normal pesto using Thai basil, but that would be just too weird. Thai basil is its own thing. It really isn't a substitute for other basils.
So, embrace the Thai-ness of it. Make Thai basil pesto. I know that sounds weird, but it's weird in a good way. Whereas normal pesto using Thai basil would be weird in a bad way.
So, what might that look like? Going ingredient by ingredient....
Garlic: Keep. Thai food and garlic are friends.
Pine nuts: Nope. No way. Sesame seeds would be good, but using only sesame seeds would be kind of... seedy. Almonds would be tasty, but they're too hard. Cashews have a good texture. Sesame seeds and cashews. Definitely!
Olive oil: Absolutely not! Toasted sesame oil is lovely, but a bit strong. Using part untoasted sesame oil would be lovely, but I don't have any. So, maybe walnut oil along with the toasted sesame.
Pecorino romano: Cheese? Yuck! Not for Thai pesto. Just leave it out. Or increase the nuts.
Salt: Yes. And black pepper.
So, more or less using my favorite pesto recipe, I just madke the substitutions above. Except, I've been making pesto so long, I don't use a recipe and have no idea how much of each ingredient I use. I just do everything to taste. Here are some rough guidelines:
Ingredients (quantities are very approximate):
1-2 Tbsp toasted sesame oil
2-3 Tbsp walnut oil
2 cloves crushed garlic, or 2 garlic ice cubes, plus a dash of dry roasted garlic
1 fist full of cashews
2-3 Tbsp sesame seeds
2 cups loosely packed Thai basil leaves
Sea salt & freshly ground black pepper to taste
- Pulse everything except basil, salt, & pepper until minced.
- Pulse in basil leaves, being careful not to over process.
- Add salt & pepper to taste.
- Store in refrigerator.
- Toss some with poached chicken and cooked rice noodles.
- Plop some on cooked vegies to give them a little excitement.