Prepare the Dough:

In a mixing bowl, combine the warm water, sugar, and active dry yeast. Let it sit for about 5-10 minutes until it becomes frothy.

Add the olive oil, salt, and flour to the yeast mixture. Mix until a dough forms.

Knead the dough on a floured surface for about 8-10 minutes, until it becomes smooth and elastic.

Place the dough in a lightly oiled bowl, cover with a damp cloth, and let it rise in a warm place for about 1 hour, or until doubled in size.

Prepare the Filling:

In a large skillet, heat the olive oil over medium heat.

Add the chopped green onions, grated carrots, shredded cabbage, and chopped bell peppers. Sauté for about 5-7 minutes, until the vegetables are softened.

Add the boiled and mashed potatoes to the skillet, and mix well with the vegetables.

Season the mixture with salt, black pepper, paprika, and dried oregano. Stir to combine.

Remove from heat and let the filling cool slightly. If using, mix in the grated mozzarella cheese.

Assemble the Bread:

Preheat your oven to 375°F (190°C).

Punch down the risen dough and transfer it to a floured surface. Roll it out into a large rectangle, about ¼ inch thick.

Spread the vegetable filling evenly over the dough, leaving a small border around the edges.

Carefully roll the dough up, starting from one of the long edges, to form a log. Pinch the seams and ends to seal.

Place the rolled dough on a parchment-lined baking sheet. Make a few slashes on the top with a sharp knife for steam to escape.

Bake in the preheated oven for about 25-30 minutes, or until the bread is golden brown and sounds hollow when tapped.

Let the bread cool slightly before slicing.

Serve warm, and enjoy your delicious Vegetable Filled Bread!