Heat a large, deep skillet with a lid over medium-high heat. If using, add prosciutto in a single layer and cook until curling and browned underneath, about 2 minutes. Flip over and let cook until browned on the other side. Transfer to a paper towel to blot oil and cool.
Add oil to the same skillet and heat it for a minute. Add frozen tortellini in a single layer and cook for 2 to 4 minutes, until they’re browned underneath.
Sprinkle with frozen peas and add water to the pan. Put the lid on, and let them steam for about 5 minutes. If the water cooks off too quickly, add a splash more.
At 5 minutes, all water should have cooked off. Scoop pasta and peas into a bowl. If any pasta has stuck, add a splash more water over high heat to deglaze them off.
Dollop on crème fraîche so it melts over the pasta. Squeeze lemon juice over, then sprinkle with salt, pepper, crumble prosciutto over (if using), then slivers of mint and parmesan, if desired.
