Add the beef and saute, stirring occasionally, until brown on all sides, about 5 minutes. Add wine and thyme, stir well, and bring to boil.
In heavy, large pot over moderately-high heat, bring stock to a boil. Lower the heat to moderate and gradually whisk in the polenta, stirring constantly. Continue cooking, stirring constantly, until polenta thickens and pulls away from sides of pan, about 5 minutes. Transfer the polenta to an oil-coated serving bowl and keep warm. Let the polenta sit for 5 to 10 minutes so it can set up.
Turn the polenta out of the bowl, slice, and serve alongside the stew.