For the chicken: Marinate the chicken in the Balsamic Base for at least 30 minutes or up to 2 hours in the refrigerator.
Preheat a grill pan or grill over medium-high heat.
Let any excess marinade drip off the chicken, and then grill the chicken for 5 to 6 minutes per side until cooked through. Once cooked, let rest 5 to 10 minutes. Then slice thinly on the bias.
For the spinach and artichoke spread: Squeeze the drained spinach with a kitchen towel to dry it out. Place into a food processor with the sour cream, mayonnaise, garlic, lemon zest and juice. Puree until smooth. Taste for seasoning and add the artichokes. Pulse 2 to 3 times to leave the artichokes slightly chunky.
For the sandwich build: Cut the Fresh Focaccia in half equatorially. Spread each half with Spinach Artichoke Spread. Then, on the bottom of the bread, sprinkle over the sliced sun-dried tomatoes, top with chicken slices, place a layer of mozzarella down and top with arugula. Place on the other half of bread and cut into as many pieces as you like and enjoy!
Heat the balsamic vinegar in a heavy-bottomed saucepan over medium heat. Add the brown sugar, salt, pepper, basil, thyme, garlic and shallots into the saucepan and stir. Bring the mixture to a gentle simmer and let cook until the liquid is reduced by half, 30 to 45 minutes. Once the mixture is reduced, strain it through a fine mesh strainer set over a bowl and let cool. Store the balsamic base in the fridge; it's great in salad dressings, marinades, drizzled over steaks...let your imagination run wild.
Place the water in the bowl of a stand mixer. Add the sugar, sprinkle the yeast over the water and let it bloom until bubbly, 5 to 15 minutes.
In a mixing bowl, combine the all-purpose and wheat flours together with the salt and chopped rosemary. Gradually add the flour mixture to the bloomed yeast in the mixing bowl. Then add 1/2 cup of the olive oil.
Using the dough hook attachment, mix the dough on medium speed until it becomes smooth and soft, 8 to 10 minutes. The dough will be very loose.
Transfer the dough to a clean, floured surface and knead the dough by hand for 2 to 3 minutes.
Wipe out the bowl you mixed the dough in and then coat the bowl with some olive oil. Return the dough to the oiled bowl and let it rest in a warm place, covered with a dish towel, until doubled in size, 30 to 35 minutes.
Oil a 9-by-13-inch baking sheet with the remaining 1/2 cup olive oil. Spread the dough into the pan using your fingertips to create dimples into the dough. The more dimples you make, the more texture the bread will have.
Using a pastry brush, oil the dough and place leaves of rosemary into some of the dimples. Top with the tomato slices and sprinkle with the Parmesan. Cover the dough again with the towel and let rest in a warm spot until doubled in size, another 30 minutes.
Preheat the oven to 425 degree F and set a rack in the middle of the oven.
Bake the dough until golden brown, 35 to 40 minutes.