Now, people across the country can bake the indulgent cookies at home. Last week, Whole Foods stores across the country started carrying frozen versions of Levain cookies. The frozen cookies are available in three varieties: Chocolate chip walnut, two chip chocolate chip and dark chocolate chocolate chip. It’s the latest example of a local restaurant trying to cash in on a wider audience for its products at the grocery store. The approach comes with challenges but potentially big rewards.Restaurants that