Prep garlic chips: Thinly slice large garlic cloves using a mandolin or sharp knife into even slices. Spread out to dry while prepping other ingredients.
Prep lime leaves: Wash kaffir lime leaves thoroughly and dry completely to avoid oil splatter. Remove center stems and tear each leaf into 4 stem-free pieces.
Prep lemongrass and chilies: Thinly slice lemongrass stalk on diagonal. Prepare dried chilies (about 6 pieces).
Make seasoning powder: Combine salt, sugar, lime juice powder, cayenne pepper (optional), and chicken bouillon powder (optional) in a coffee grinder or spice grinder. Grind to a fine powder for better adherence to nuts.
Fry herbs in oil: Heat about 1 inch of vegetable oil over medium heat. Test oil temperature with one garlic slice; when it bubbles, add remaining garlic slices and reduce heat to low. Fry garlic gently until crispy and golden but not browned. Remove and drain on paper towel. Next, fry lime leaves on low heat until crispy (bubbles subside). Remove. Then fry lemongrass slices on low heat just to infuse flavor; do not eat them, remove and discard after bubbles subside. Finally, fry dried chilies on low heat until slightly darker and crispy, about seconds.
Fry peanuts and cashews: Increase oil heat to medium-high (about 350°F/175°C). Add raw peanuts first, ensuring they are submerged in oil. Stir constantly for even cooking. Fry small peanuts about 7 minutes, larger ones up to 10 minutes, until golden brown but not overcooked. Remove and drain on paper towel-lined pan for faster cooling. Then fry cashews in same oil for 3-5 minutes until golden. Remove and combine with peanuts.
Season and toss: While nuts are still hot and oily, sprinkle the seasoning powder generously over them. Toss well to coat evenly. Add fried garlic chips, lime leaves, and dried chilies to the nuts and toss again.
Cool and serve: Allow the nut mixture to cool completely for about 15 minutes to become crunchy. Serve as a snack or party appetizer.