Ingredients
Scale
The Chocolate Batter
- ½ cup (115g) unsalted butter, cut into pieces
- 4 oz (115g) dark chocolate (60–70% cacao), roughly chopped
- 1 cup (200g) granulated sugar
- ¼ cup (50g) packed brown sugar
- 3 large eggs, at room temperature
- 2 additional egg yolks, at room temperature
- 1 tsp pure vanilla extract
- ½ cup (50g) Dutch-process cocoa powder
- ⅓ cup (40g) all-purpose flour
- ½ tsp salt
- 1 tsp espresso powder (optional but strongly recommended)
The Nutella Center
- 1 cup (300g) Nutella, at room temperature or slightly warmed (15 seconds in microwave)
For Finishing
- Flaky sea salt, for scattering generously
- Crushed toasted hazelnuts (optional)
- Powdered sugar for dusting (optional)
- Extra warm Nutella for drizzling over each serving
For Serving
- Vanilla bean ice cream
- Fresh raspberries
- Whipped cream (optional)
Instructions
- Prepare the slow cooker. Line the slow cooker insert with parchment paper — a circle on the bottom and a strip around the sides with overhang handles for easy removal. Grease the parchment lightly with butter or cooking spray.
- Melt the chocolate and butter. In a medium saucepan over low heat or in a microwave-safe bowl in 30-second intervals, melt the butter and chopped dark chocolate together, stirring until completely smooth. Remove from heat and let cool for 5 minutes.
- Add the sugars. Whisk the granulated sugar and brown sugar into the warm chocolate mixture until fully combined.
- Add the eggs and vanilla. Add the eggs and egg yolks one at a time, whisking well after each addition until the batter is smooth and glossy. Stir in the vanilla extract.
- Add the dry ingredients. Sift the cocoa powder, flour, salt, and espresso powder (if using) into the chocolate mixture. Fold gently with a rubber spatula until just combined — do not overmix. The batter will be thick, glossy, and deeply dark.
- Layer the bottom batter. Pour approximately half of the chocolate batter into the prepared slow cooker insert and spread into an even layer. This is the base of the cake.
- Add the Nutella center. Spoon the Nutella in generous dollops over the center of the bottom batter layer. Using the back of the spoon, spread it carefully into an even layer, leaving a 1-inch border around the edges where the batter will seal the Nutella in during cooking. Be generous — this is the lava.
- Add the top batter layer. Carefully spoon the remaining chocolate batter over the Nutella layer, spreading gently from the edges inward until the Nutella is completely covered and sealed. The top batter layer should be even and smooth.
- Set up the slow cooker. Lay 2 full sheets of paper towels flat across the top of the slow cooker opening. Place the lid on top of the paper towels, securing them between the lid and the rim.
- Cook. Set the slow cooker to HIGH. Cook for 2 to 2.5 hours without lifting the lid. Begin testing at the 2-hour mark. The cake is done when the edges are set and pulling slightly away from the sides, the top has a matte, set surface, and the center has a slight wobble but is not liquid when the insert is gently shaken.
- Finish. Scatter flaky sea salt generously over the surface of the cake immediately after cooking. Dust lightly with powdered sugar if desired. Scatter crushed toasted hazelnuts if using.
- Serve immediately. Bring the slow cooker to the table. Using a large, deep spoon or ice cream scoop, scoop generous portions into warm bowls, making sure each serving includes cake from the top layer, a flow of Nutella from the center, and cake from the bottom layer. The Nutella will flow out into the bowl as the portion is served. Finish each bowl with a scoop of vanilla bean ice cream, a few fresh raspberries, and a drizzle of warm Nutella. Serve at once.
Notes
- Room temperature eggs are essential. Cold eggs can cause the melted chocolate and butter to seize and clump when whisked together. Take the eggs out of the fridge at least 30 minutes before starting.
- Warm the Nutella before using. Cold Nutella is thick and difficult to spread without disturbing the bottom batter layer. Room temperature or slightly warmed Nutella spreads smoothly and evenly, creating a clean, distinct center layer.
- Leave a border around the Nutella. Spreading the Nutella to the very edges of the insert means it can merge with the top batter layer during cooking and lose the distinct flowing center. A 1-inch border of batter around the Nutella ensures it stays sealed and flows properly when served.
- The paper towel trick is essential. Used here for the final time in this dessert series — two sheets of paper towels between the lid and the slow cooker rim absorb condensation and keep the top of the cake from getting wet and steamed during cooking.
- The center wobble means it is right. A perfectly cooked lava cake has a set outer layer and a soft, slightly yielding center that wobbles gently. If the center looks completely firm, the Nutella has set too much and the lava effect will be diminished — serve immediately without further cooking.
- Serve immediately and into warm bowls. The Nutella flows most dramatically when the cake is hot. As it cools, the Nutella sets and the lava effect reduces. Warm bowls keep it flowing longest.
- The espresso powder does what it always does. One teaspoon deepens and intensifies the dark chocolate flavor without adding any coffee taste. It has earned permanent inclusion in every chocolate recipe in this series.
- Prep Time: 20 minutes
- Cook Time: 2 hours 15 minutes (on HIGH)
- Category: Dessert
- Method: Slow Cooking
- Cuisine: American
- Diet: Vegetarian