Line 2 baking sheets with wax or parchment paper. Place 2 smaller spoons and a knife on top (so it’s all ready to go) or grab a medium cookie scoop if you have one. Set aside near by.
In a large bowl of an electric mixer, add the egg whites and vanilla. Add the beater attachment and plug in the mixer so it’s ready to go.
In a large sauce pan, combine the sugar, karo syrup and water over medium heat. Bring to a boil and stir constantly so it doesn’t burn. If the sugar starts to come up on the edges, use a pastry brush dipped in hot water to wipe it down. Clip a candy thermometer to the pan.
While the mixture is boiling, start whipping the egg whites with vanilla in the mixing bowl. Beat until a stiff peak forms. Leave the beaters on as we’ll add the sugar mixture into this bowl.
Once the candy mixture reaches 240°F, turn the heat to medium-high and drizzle about half the mixture SLOWLY into the bowl with the egg whites. Place the sauce pan back on medium high heat until it reaches 260°F. Scrape the downsides of the mixer and mix on high speed. When the remainder of the sugar mixture reaches 260°F, slowly pour into the egg white mixture. Scrape down the sides and then beat on high speed until the candy loses its glossy finish (about 5-10 minutes). When the beaters are lifted up, the candy shouldn’t drizzle off. Test a spoonful on a piece of wax paper. If it begins to flatten, keep mixing on high and check another spoonful after a minute. Fold in pecans if desired.
Once it’s ready, you need to move fast or it will harden quickly. Take your spoons or cookie scoops and scoop onto the paper. Allow 1 hour to set.
Store in a covered container at room temperature for 2 weeks or in the freezer for 3 months.