Preheat the oven to 180C/350F/Gas 4. For the relish, heat a small frying pan over a medium heat and add the olive oil. Stir in the tomatoes, garlic infused oil and the vinegar.
Gently simmer for five minutes, or until the mixture has thickened to a relish consistency. Taste and adjust the seasoning as necessary. Leave to cool.
For the rest of the burger, place the sliced eggplant onto an oven tray, drizzle with the oil and season with salt and pepper. Bake in the oven for 10 minutes, or until beginning to soften.
Alternatively, you can brush the eggplant slices with olive oil, then griddle.
Meanwhile slice the mozzarella ball into four equal slices. After the eggplant has cooked for 10 minutes, remove from the oven and place a slice of mozzarella into each of the eggplant slices on top of the stalk. Put back into the oven for 5-7 minutes to melt the mozzarella.
To assemble, lightly toast the cut side of the gluten free burger buns. Spread with a little relish and then place the eggplant on top of the bottom gluten free burger bun.
Top with the salad leaves, tomato slices and add any remaining relish on top. Finish by sandwiching each burger with the remaining halves.