Combine the Herb Ricotta mixture in a bowl and set aside.

In a skillet, heat 1 tbsp. olive oil and sauté the finely diced onion until softened for about 5 minutes. Add garlic and cook for 1 more minute. Set aside to cool.

In a large bowl, mix egg, half and half, breadcrumbs, Parmesan, parsley, Italian seasoning, mustard powder, and ¾ cup of the herb Ricotta mixture. Add the cooled onions and garlic.

Season the meat with salt and pepper, then add it to the bowl. Gently mix until well-combined. Avoid overworking the meat.

Roll the mixture into 1 ½-inch meatballs and refrigerate for 15 minutes.

Heat the remaining oil in a large skillet over medium-high heat. Brown the meatballs in batches for about 1 ½ minutes per side. Set aside.

Remove excess oil from the skillet and pour in the marinara sauce. Add water (about ¼+ cup) to prevent the sauce from thickening too much.

Return the meatballs to the skillet, spoon sauce on top, and cook for 30 minutes over medium heat, partially covered.

Use a small cookie scoop to dollop the remaining herb ricotta mixture on top during the last 15 minutes.

Garnish with parsley and serve.