Heat sufficient water in a deep non-stick pan. Add potatoes, garlic and salt and bring to a boil. Lower heat and simmer for 10 minutes. Drain and set aside.
Heat a non-stick pan. Add the potatoes and garlic and stir on medium heat for 1 minute or till dry.
Add 3 tablespoons polenta, parsley and thyme and mash everything together with a masher, taking care that the mixture is chunky. Remove from heat and set aside in a bowl.
Whisk together egg, egg yolk, milk and 1 tablespoon olive oil in another bowl.
Stir the mixture into potato mixture, add salt and crushed peppercorns and mix well. Cover and refrigerate for 1 hour or overnight.
Spread remaining polenta on a plate.
Divide the chilled potato mixture into 12 equal portions, stuff each with a cheese cube and shape into ¾ inch diameter cakes. Coat them with polenta.
Heat some olive oil in a non-stick pan. Shallow-fry the cakes, turning sides, till golden brown and evenly done on both sides.