But either use the yoghurt (um, authentic to the
modern South
) or sour a half liter of plain milk with 30ml (two tablespoons) of either lemon juice or white vinegar -- this halves easily, think a tablespoon to a cup and let it stand five minutes before using. You can also simply stir some yoghurt into milk, 1:1. What you're trying for is milk + acidic zing. Makes the baking soda really go to work.
There are two basic kinds of American cornbread: Southern, which is simply a starch food and unsweetened, and Northern, which prefers to make cornbread sweet, though not as sweet as cake, which it otherwise rather resembles. What's the difference? Adding sugar. Whichever is eaten isn't, I think, rigidly observed by region, but professional Southerners (like professional Texans, but they sound a little different, as each Southern state has its own variation on the southern accent) will likely acknowledge that unsweetened cornpone is the traditional variety in their neck of the woods.
Oh, and frying polenta or cornbread, a/k/a cornpone, in bacon fat IS authentically Southern -- though it's the sort of thing you'd do before going out and plowing the bottom forty acres, the kind of thing Goodman John would have eaten a Ploughman's Lunch to fuel up for. Oldfashioned, that is.
Those chili peppers are optional, for a spiced cornbread. If you go with the chilis, you might consider grating some cheddar cheese on top.