Bring the water, milk, and salt to a boil. Slowly whisk in the polenta. Turn heat to low, and continue whisking for 5 minutes, or until polenta is smooth and creamy. Spread the polenta in a 9x9 baking dish, and set aside to cool.
While the polenta is setting up, add the butter and olive oil to a heavy-bottomed skillet set to medium-low heat. Add the sliced onions and a sprinkle of kosher salt, and cook, stirring occasionally until soft, golden, and caramelized- about 20-25 minutes.
Pour 1 tablespoon olive oil into another skillet, set over medium heat. Using a 3" round cookie cutter, cut out circles of the firm polenta, and place in the heated skillet. Cook until slightly browned and crusty on one side, about 2 minutes, then flip and cook the other sides another two minutes.
To assemble the polenta cakes, place on a plate, add one tablespoon of caramelized onions to each cake, top each with about a teaspoon of crumbled goat cheese, and drizzle with honey. Enjoy!