WIth hands, gently combine all ingredients through cilantro. Make into 2" balls and set aside.
Heat large skillet over medium-high heat and add both oils. Wait about 20-30 seconds and carefully place meatballs in pan. Don't overcrowd the pan. Leave a little room so they're not touching. You'll be cooking these in a couple of batches so it's all good.
Lower heat to medium and cook meatballs approximately 2-3 minutes on each side. You want them golden brown before flipping. If they stick to the pan, they aren't ready. They'll release when they're ready.
As each batch is cooked on both sides. remove the meatballs to paper towel lined plate or rimmed baking sheet. You don't want those babies rolling away. And no testing because they're not cooked all the way through yet.
Time to make the sauce.
For the Sauce
In the same pan, raise the heat to medium-high and add the olive oil. Once heated, add the chopped onions and cook for about 5 minutes. After they are golden brown and translucent, add the garlic and saute until you can smell it for about 30 seconds.
Add the chicken broth and stir in the red curry paste, coconut milk and fish sauce.
Reduce the heat to a simmer and let the sauce come together for 5 minutes, stirring occasionally.
Gently add the meatballs to the sauce, cover the pan and cook over low heat for 10-15 minutes until thoroughly cooked through.
Meanwhile, put the cornstarch in a small bowl and set aside.
Once the meatballs are cooked through, remove about 1/4-1/3 cup of the simmered sauce into the bowl with the cornstarch and stir completely to make a slurry. Add the slurry back into the skillet to thicken the sauce.