Yield: 2 cups.
1 pound thick-cut bacon, cut crosswise into 2-inch pieces
2 cups yellow onion, diced
1 teaspoon kosher salt, plus more as needed
¼ cup packed dark brown sugar
3 cups chicken broth, divided
2 tablespoons molasses
¼ teaspoon ground cayenne pepper
Place the bacon pieces in a large, heavy-bottomed pot or Dutch oven over medium heat and cook, stirring occasionally, until the fat has rendered and the bacon starts to brown.
Add the onion and salt, and cook, stirring occasionally, until the onion has browned, about 5 minutes. Add the sugar and stir to combine.
Add 1 cup of the broth or stock and bring it to a simmer, scraping up the browned bits from the bottom of the pot. Continue to simmer, stirring occasionally, until the mixture has thickened and almost all of the liquid has evaporated, about 8 to 10 minutes.
Add the remaining broth, molasses, and cayenne pepper and stir to combine. Simmer, stirring occasionally, for 20 minutes. Remove from heat and allow to reach room temperature.
Transfer the mixture to a blender and reserve the pot. Blend until smooth, or to desired consistency.
Return the mixture to the reserved pot, place it over medium-high heat, and cook, stirring occasionally, until it’s reduced to about 2 cups. Remove from the heat. Cool to room temperature and refrigerate in an airtight container for up to 2 weeks. Warm before using.