Prepare the Cupcakes:

• Preheat the oven to 350°F (175°C). Line a 12-cup muffin tin with cupcake liners.
• In a medium bowl, whisk together the flour, cocoa powder, baking powder, baking soda, and salt. Set aside.
• In a large mixing bowl, beat the softened butter and granulated sugar together with an electric mixer until light and fluffy, about 2-3 minutes.
• Add the eggs one at a time, mixing well after each addition, then stir in the vanilla extract.

2. Combine Wet and Dry Ingredients:

• Gradually add the dry ingredients to the wet ingredients, alternating with the buttermilk. Start and end with the dry ingredients. Mix until just combined.
• Slowly stir in the boiling water to thin the batter (it will be quite thin). If using, fold in the chocolate chips for an extra gooey chocolate flavor.

3. Make the Peanut Butter Lava Filling:

• In a separate small bowl, beat together the peanut butter, powdered sugar, softened butter, vanilla extract, and salt until smooth and creamy.
• Scoop about 1 tablespoon of the peanut butter mixture into the center of each cupcake liner, right into the middle of the batter.

4. Fill the Cupcake Liners:

• Spoon the chocolate batter over the peanut butter mixture, filling each cupcake liner about 2/3 of the way full. Be sure to cover the peanut butter completely so it’s hidden inside the cupcake.

5. Bake the Cupcakes:

• Bake in the preheated oven for 18-20 minutes, or until a toothpick inserted into the edge of a cupcake comes out clean. Be sure to check the center of the cupcakes; if it’s still gooey, give it a couple more minutes. The peanut butter center should remain soft and molten.
• Let the cupcakes cool in the pan for about 5 minutes, then transfer them to a wire rack to cool completely.

6. Serve:

• Once cooled, you can enjoy the cupcakes as they are or drizzle them with melted chocolate or extra peanut butter for added indulgence.