2) Melt the butter in a very large saute pan and saute the corn and onion over medium-high heat for 4 minutes. Cool slightly.
3) Whisk together the eggs, milk, and single cream in a large bowl. Slowly whisk in the polenta and then the ricotta. Add the basil, caster sugar, salt, and pepper. Add the cooked corn mixture and grated cheddar, and then pour into the baking dish. Sprinkle the top with more grated cheddar.
4) Place the dish in a larger pan and fill the pan 1/2 way up the sides of the dish with hot tap water. Bake the pudding for 40 to 45 minutes until the top begins to brown and a knife inserted in the center comes out clean. Serve warm.