Preheat your oven to 375°F (190°C). Lightly grease a 9x13-inch baking dish. Spread 1/2 cup marinara over the bottom to prevent sticking.

Make the fathead dough. In a microwave-safe bowl, combine 1 1/2 cups mozzarella and cream cheese. Microwave in 20–30 second bursts, stirring between each, until fully melted and smooth. Stir in almond flour and salt, then mix in the beaten egg until a cohesive dough forms.

Shape the shells. Place the warm dough between two sheets of parchment and roll to about 1/8-inch thick. Peel the top parchment and use a 3 1/2–4-inch round cutter (or a glass) to cut circles. Re-roll scraps as needed to get 10–12 rounds. Set aside on parchment.

Make the filling. In a bowl, combine ricotta, spinach, Parmesan, egg, Italian seasoning, garlic, salt, pepper, and a pinch of nutmeg if using. Mix until smooth and thick. The mixture should hold its shape on a spoon.

Assemble. Place about 1 1/2 tablespoons of filling in the center of each dough circle. Gently fold two sides up to meet, creating a “shell” or taco shape that cradles the filling. Pinch the top edges just slightly to help them hold. Arrange in the prepared dish, open-side up.

Top with sauce and cheese. Spoon the remaining marinara over and around the shells. Sprinkle with 1 cup shredded mozzarella.

Bake for 18–22 minutes, until the cheese is melted and bubbling and the edges of the shells look lightly golden. If desired, broil for 1–2 minutes to brown the top.

Rest and garnish. Let the dish rest for 5–10 minutes to firm up. Sprinkle with fresh basil or parsley and serve warm.