Add the milk and heavy cream to a medium saucepan and bring to a low boil, stirring constantly so the milk doesn't scorch. Whisk in the polenta, whisking constantly until smooth. Stir in a big pinch of salt. Reduce the heat to medium low and cook, stirring frequently, until the polenta is tender, about 30 minutes.
Meanwhile, add the bacon to a medium pan. Turn the heat to medium high and cook, flipping once, until the bacon is crispy, about 10 minutes. Remove the bacon to a paper towel-lined plate to drain. Add the shallot to the pan and cook until translucent, about 2 minutes. Add the chard and a big pinch of salt and cook until wilted but still crisp-tender, about 7 minutes. Stir in a shake of hot sauce if desired. Chop the bacon, add it to the greens and stir to combine. Remove from the heat.
Add a big pinch of black pepper to the polenta and stir. Taste and adjust for salt and pepper. Remove the polenta from the heat and stir in the butter. Transfer to a serving plate and top with the greens in the center.