Midnight Decadence: Just 4 ingredients. I love making it when I want a rich treat handled hours ahead of dinner.

This little slow cooker dessert is what I reach for when the afternoon is quiet, supper is still a few hours off, and I’m craving something truly rich that will be ready and waiting. I call it a 4-ingredient obsidian fudge, because it settles into a dark, glossy pool that bubbles and cracks on top while the inside stays molten and gooey. It reminds me of the hot fudge puddings my mother baked in the farmhouse oven, but this version is even simpler and hums along in the slow cooker while you tend to the rest of dinner or putter in the garden. It’s pure Midwestern comfort: practical, make-ahead, and deeply chocolatey.

Serve this midnight fudge warm right from the slow cooker, spooned into small bowls so everyone gets some of the cracked, crinkly top and the molten center. A scoop of vanilla ice cream or a spoonful of lightly sweetened whipped cream is lovely against all that richness, and a hot cup of coffee or cold glass of milk fits right in with the old-fashioned supper table feel. It’s quite intense, so small portions go a long way, and you can keep the slow cooker on warm so folks can come back for a second spoonful later in the evening.

Servings: 6–8

2 cups semi-sweet chocolate chips (about 12 oz)

Lightly grease the inside of a small slow cooker (about 3–4 quarts) with a little butter or nonstick spray. This helps the fudge pull away from the sides and encourages that cracked, crinkly top as it cooks.

Add the chocolate chips, sweetened condensed milk, and butter pieces to the slow cooker. Stir them together just enough to roughly combine; it will look streaky at this point, and that’s fine.

Cover the slow cooker with its lid and set it to LOW. Cook for 1 1/2 to 2 hours, until the mixture is glossy around the edges and bubbling in the center. You should see a dark, almost obsidian surface with little bubbles breaking through.

Remove the lid and quickly stir in the vanilla extract until fully blended. The mixture will be very thick and dense, almost like lava. Smooth the top a bit with a heatproof spatula, but don’t worry about making it perfect.

Cover again, leaving the lid slightly ajar with a wooden spoon or folded towel to allow a little steam to escape. Continue cooking on LOW for another 30–45 minutes. During this time, the top will set, crack, and become crinkly, while the interior stays gooey and molten.

Once the surface looks set with visible cracks and slow, thick bubbles pushing up here and there, switch the slow cooker to WARM. Let the fudge rest for at least 15 minutes with the lid off; it will thicken slightly but remain soft and spoonable.

Serve the obsidian fudge warm, spooned straight from the slow cooker into small bowls. Be careful of the hot ceramic insert and very hot fudge. Any leftovers can cool completely in the insert, then be transferred to a covered container and stored in the refrigerator.

For a darker, more intense chocolate, replace 1/2 cup of the semi-sweet chips with bittersweet or dark chocolate chips; this will deepen the color and flavor into a true midnight treat. If you like a little crunch, you can stir in up to 1/2 cup of chopped toasted pecans or walnuts along with the vanilla, keeping in mind this will add a fifth ingredient. A pinch of kosher salt or a light sprinkle of flaky salt over the finished fudge will highlight the chocolate and give it an old-fashioned fudge-shop feel. If you prefer a softer, sauce-like texture for drizzling over ice cream, shorten the second cooking time by about 15 minutes so it doesn’t set quite as firmly on top. For food safety, always cook this on LOW, not on the keep-warm setting, so the mixture heats evenly and thoroughly. Use oven mitts when handling the slow cooker insert, as it becomes very hot, and keep children away from the counter edge while the fudge is bubbling. Cool leftovers promptly and refrigerate within 2 hours; rewarm gently in the slow cooker on LOW or in short bursts in the microwave, stirring often so it heats evenly without scorching.