In a small bowl, combine Sauce ingredients. Set aside.
In a non-stick pan on medium heat, add sugar followed by water. Stirring constantly, bring to a simmer.
Once the syrup thickens and can coat the back of your spatula, quickly add walnuts. Quickly mix to coat evenly.
Once coated and a crust has formed around each walnut, immediately remove pan off the heat and remove candied walnuts one by one with tongs and transfer to parchment paper spreading them apart. Set aside.
In a large bowl, add peeled and deveined shrimp, season with salt and black pepper.
In a separate large bowl, add egg whites and whisk until foamy. They should just be foamy, not like a meringue. Add cornstarch and mix until you have a runny paste.
Add seasoned shrimp and mix well until shrimp is coated in batter with tongs or chopsticks.
Heat vegetable oil or any neutral oil in a large pan on medium-high heat. Once it’s hot (around 350-375 degrees F), fry shrimp in small batches for 2-3 minutes until crispy and a golden brown color develops. Do not overcrowd the pan.
Remove shrimp from hot oil with a slotted spoon or tongs and transfer to wire rack or paper towel lined baking sheet to drain off excess oil.
In a large bowl, add crispy shrimp, candied walnuts, followed by sauce. Toss everything together. Garnish with green onions.