Prepare a couple sheet pans by lining with parchment and two spoons that are greased and set aside
In a large saucepan, combine the water, corn syrup and sugar then stir to combine
Set your candy thermometer and continue to stir occasionally until the mixture begins to boil (Once the mixture just starts to boil, stop stirring and do not stir again)
Meanwhile, in the bowl of a stand mixer, whip the egg whites at med/high speed until stiff peaks and set aside until the syrup mixture is ready
Once the syrup mixture reaches 250 degrees or firm-ball stage, remove from the heat
Turn on the mixer with the egg whites and turn the speed to medium
***Very, very slowly - and carefully - pour a slow, steady stream of the hot syrup into the whipped egg whites. It should take about 5 minutes to pour the syrup into the eggs - do no rush it! Pour the mixture while the mixer is running. Do not stop/start to pour.
Keep speed at 2 (low) and keep mixing until the divinity no longer drips from the whisk. WATCH CLOSELY, you don't want to over mix
Once the entire syrup mixture has been poured and it’s been combined, add the vanilla.
Remove the bowl from the stand mixer and add in the chopped walnuts or pecans and fold into the mixture
Scoop out a spoonful of the mixture and use the other spoon to scrape it off. Drop the dollops onto the parchment and continue until the rest of the mixture has been portioned out
Add a pecan or walnut half on top of each mound and press into place
Allow them to set for about 30 minutes to firm up