Make the filling: Heat the olive oil in a medium saute pan. Add the chopped onion, frying until soft and translucent, 3-4 minutes. Add the chopped tomatoes and their juices, cooking until lightly simmering. Add the eggplant. Season with the sugar, salt, and pepper. 

Simmer for around 20 minutes, stirring occasionally to avoid sticking. The liquid should be absorbed — if the mixture is still wet, cook for a bit longer. Place the mixture into the refrigerator to cool. Once cooled, mix the parsley into the filling.

Make the pastry dough: In a medium saucepan, bring water, oil, and salt to a boil. Remove from heat. Mix in flour, 1 cup at a time, stirring until a firm dough forms.

On a lightly floured surface, knead the dough until soft and flour is fully incorporated. Divide the dough into 3 pieces. Form ⅔ of the dough into 25, walnut-sized balls (2 tablespoons). Form the remaining dough into 25 smaller balls (around 1 tablespoon) to be used for the tops of the pastelikos.

Preheat the oven to 350F and prepare a sheet pan with parchment paper. Form one the larger balls into a cup shape, using your thumb to shape the dough. Fill the opening with a heaping tablespoon of eggplant filling.

Flatten one of the smaller balls and use it to cover the eggplant filled cup. Pinch the edges together and crimp them until fully closed, using your thumb and forefinger to fold the edges over. Repeat with remaining portions of dough.

Brush the tops of the pastelikos with egg wash and sprinkle with sesame seeds. Place the parchment lined baking sheet and bake for 25-30 minutes, until crisp and lightly browned. Remove from oven and let cool on wire racks.