Preheat the oven to 400 degrees.
Prepare a baking sheet by either lining with parchment paper or spraying lightly with cooking spray. Set the prepared baking sheet aside.
Heat the olive oil in a large skillet over medium heat. Add the ground beef and onion. Cook, stirring frequently, until the beef shows no more pink color. Add the garlic and cook for 1 additional minute. Drain well and return to the pan.
Add the tomato paste, water, salt, pepper, and Italian seasoning. Cook, stirring for 2-3 minutes or until the water has nearly evaporated. Remove pan from the heat and stir in the Parmesan cheese. Set the mixture aside to cool a bit while preparing the crescent rolls.
Open the crescent rolls and unroll them on a work surface. Separate each package of rolls into four rectangles (each rectangle will contain 2 crescent rolls). Press the perforations in each rectangle together.
Place ⅛ of the beef mixture (about 2 generous tablespoonfuls) on the end of each rectangle leaving about an inch all the way around in order to seal the packages. Fold the unfilled end over the filled end. Using a dinner fork, seal the three open edges.
Place the filled hand pies on the prepared baking sheet.
In a small bowl, use a fork to whisk together the egg and water. Brush lightly over the hand pies. Use a small sharp knife to cut a slit in the top of each pie.
Bake in preheated oven for 5 minutes. Reduce the heat to 375 and continue cooking for an additional 5-7 minutes or until golden brown all over.
While the hand pies are cooking, warm 2 cups of purchased marinara sauce in a small pan over medium-low heat.
Remove from the oven and allow to cool for 5 minutes. Serve with a side of warm marinara sauce for dipping.