In a saucepan of boiling salted water, cook 3 cups of the peas until tender, 3 minutes. Drain and transfer to a food processor. Add the yogurt, tarragon and vinegar and process to a chunky puree. Add the cream and pulse to blend; transfer to a saucepan and reheat. Season with salt, pepper and cayenne. Spoon the porridge into bowls. Top with the ricotta, ham, pea shoots and remaining peas; serve.