1Heat the oven to 400°F and arrange a rack in the middle. Coat the wells of 2 6-well muffin top pans or 1 standard 12-well muffin pan with bacon drippings (or vegetable oil); set aside.
2Combine cornmeal, flour, sugar, baking powder, salt, and baking soda in a large bowl and whisk to aerate and break up any lumps.
3In a medium bowl, combine butter, buttermilk, eggs, and thyme and whisk until incorporated and smooth.
4Add wet ingredients to dry, stirring just until incorporated, about 1 minute. Divide batter evenly (about 1/3 cup) among the wells, and sprinkle about 1 heaping teaspoon of bacon over each muffin top.
5Bake muffin tops until golden and a toothpick inserted in the center comes out clean, about 15 minutes. Let sit in the pans 5 minutes before removing.