Over medium heat, in a large saucepan with extra virgin olive oil, saute the garlic and onion for 1 minute.
Add all the vegetables then saute them for about 15 minutes.
Add the soy sauce, salt and pepper then toss for 1 minute. Set aside.
Make the rolls by laying 2 squares of filo (1 square can easily break) on the working area. Spoon some vegetables at the part closer to you. Roll, tuck in the sides then keep on rolling until the end. Wet your fingertips with water then dab the ends of the filo lightly to seal them. Work on the other spring rolls.
Line a baking tray with parchment paper and place the spring rolls on it.
Brush each spring roll with extra virgin olive oil.
Bake for 15 minutes or until they turn golden brown.
Meantime, while the spring rolls are cooking, prepare the sauce. Over low - medium heat, in a small saucepan, combine the water and sugar and let it boil. Add the vinegar and soy sauce. Cook for about 15 minutes then season with the pepper. Get a couple of tablespoons of the sauce and put it in a small cup or bowl. Mix it well with the cornstarch avoiding any lumps. Mix in the cornstarch mixture with the rest of the sauce in the saucepan. Keep on cooking until it thickens.
Sprinkle the sesame seeds on the spring rolls then serve them with the sauce on the side.
* Note that phyllo dough rips easily and must be handled carefully. When a piece is torn use a little olive oil or water to wet it and stick it back together. Brushing the dough with oil makes it easier to work with. To defrost phyllo dough, remove only the sheets you need and thaw overnight in the refrigerator of for 30 minutes on the counter top.