Combine the all-purpose flour and Massel Beef Style Stock Powder in a shallow dish and stir until incorporated. Set aside.
Place the beaten eggs in another shallow bowl and the panko in a third.
Dip the eggplant rounds first in the flour mixture, then the egg, then completely cover in panko. Place the prepped eggplant slice on a plate and continue the process with the remaining rounds.
Pour oil to a depth of 1-inch in a deep frying pan and heat over medium heat.
Once a few panko pieces dropped in the pan start to sizzle add some of the breaded eggplant to the oil, being sure to not over crowd the pan.
Cook until the edges are turning golden, 3-4 minutes, flip and cook another 3 minutes or so until completely golden and cooked through. Remove to a paper towel lined plate and repeat the process with the remaining pieces of eggplant.
To assemble the sandwich, melt a slice of mozzarella cheese on each side of the toasted gluten free bun under the broiler. Once the cheese has melted and is starting to brown remove from the oven and spread ½-1 tablespoon of pesto on the inside of the top of each bun then on the bottom bun layer tomato jam, 2 breaded eggplant pieces and chiffonade basil. Serve immediately.
For Summer Tomato Jam
Combine all of the ingredients in a heavy medium saucepan. Bring to a boil over medium heat, stirring frequently.
Reduce the heat and simmer, stirring occasionally, until mixture has the consistency of thick jam, about 25-30 minutes, and most of the liquid has cooked out. Taste and adjust seasoning, then cool and refrigerate until ready to use. The tomato jam will keep for at least a week in the refrigerator.