Whisk the eggs in a large bowl with herbs, cream and grated Parmigiano Reggiano cheese. Season generously with salt and pepper.
Heat the oil in a 10-inch cast-iron skillet over medium-high heat. Reduce the heat to low, pour the mixture into the skillet and cook until the edges are set but the center is still jiggly and uncooked, 8-10 minutes. Preheat the broiler.
Place the frittata under the broiler until the top is set and golden, about 2 minutes. Carefully remove the pan from the broiler, loosen the edges of the frittata and slide it onto a serving plate or a cutting board. Let cool for 5 minutes.
In the meantime, heat the Portobello Mushroom sauce according to the package instructions. Pour the sauce over the frittata, cut into wedges and serve.