1Blend ricotta and parmigiano in a small bowl and set aside.
In a heavy saucepan, bring the stock to a boil. Using a wire whisk, slowly add polenta in a thin stream, stirring constantly to prevent lumps. Reduce heat to low and cook for a couple of minutes, whisking often, until the polenta reaches the consistency of thick mush.
Stir in the corn kernels, and continue cooking and stirring until the corn is tender-crisp,
3 to 5 min.
Remove from heat and stir in the ricotta mixture, butter, and thyme if desired.