This was my favorite candy when I was growing up, and it took a while to find a recipe that came close to what I remember. A sticky mess, but so worth it! Use any flavor of jam or jelly.
Cover a large cookie sheet with parchment paper.
Butter parchment paper well, then lightly coat with cornstarch and set aside.
In a large bowl (or bowl of a stand mixer) whip egg white to soft peaks. Set aside.
Combine sugar, water, and cornstarch in a medium stockpot. Stir until all ingredients are moistened. Heat to medium, until boiling.
Using a wet pastry brush, wash down any sugar crystals from the walls of the pot.
Continue heating until the temperature reaches 260 F.
Add citric acid and grape jelly and stir until dissolved (be careful, the solution will boil up).
Continue heating until the temperature comes back to 260 F.
Turn on mixer and slowly add grape syrup to egg white.
Once added, continue to mix for another 15 minutes. The taffy should feel warm but be pourable.
Pour taffy onto prepared pan.
Using a wet spatula, or buttered hands, smooth the taffy to the edges of the pan.
Place pan in the freezer to firm up.
Remove from the freezer after about 20 minutes. Either break into uneven pieces by shattering the frozen taffy or allow to warm and cut with cooking shears.
Store between layers of parchment paper (really sticky!)