To make the syrup, heat the grape jelly in a small saucepan over medium-high heat. Dissolve the cornstarch in 2 tablespoons water in a small bowl. When the jelly has become liquid, stir in the cornstarch mixture. Simmer until a syrup consistency is reached, about 5 to 10 minutes.
In a small saucepan warm the milk over low heat. Whisk in the peanut butter and combine until completely smooth, then remove from the heat.
In a large mixing bowl add the baking mix. Stir in the eggs and milk mixture and combine until just incorporated.
Preheat the oven to 200 degrees F.
Put a large cast iron or nonstick skillet over medium heat. Spray it with cooking spray. Put 1/4 cup of pancake batter in the center of the skillet and cook until golden brown. About 1 to 2 minutes per side. When bubbles in the center of the pancake have deflated, flip over and cook the other side. Store on a sheet tray in the preheated oven to keep warm while making the rest of the pancakes.
Transfer the pancakes to a large serving platter and serve with warm grape syrup.