Prepare the pie plate and preheat the oven. Grease a 9-inch pie plate with butter or spray with nonstick cooking spray. Preheat the oven to 350°F.

Step 1. Melt the chocolate chips and butter.

Melt 2 cups of chocolate chips and cubed butter together in a microwave-safe bowl in 30-second intervals, stirring between each interval, until the mixture is smooth. Set aside to cool.

Alternatively, you can use a double boiler. Place 2 cups of chocolate chips and cubed butter in a heatproof bowl. Heat water in a saucepan over medium heat until it begins to simmer. Set the bowl over the saucepan, making sure the bottom of the bowl does not touch the water and remains at least 1 inch above it. Stir until the mixture becomes smooth.

Step 2. Beat the wet ingredients and sugar.

In a medium bowl, beat the eggs, sugar, and vanilla with an electric mixer on medium-high speed until light and creamy, about 3 minutes. Add cooled, melted chocolate and beat until combined.

Step 3. Combine with the dry ingredients.

In a separate bowl, whisk together the flour, baking powder, and salt. Add the dry ingredients to the wet mixture and fold with a spatula just until combined—do not overmix.

Step 4. Stir in the chocolate chips.

Add the remaining chocolate chips and fold with a spatula until evenly distributed.

Step 5. Bake.

Pour the batter into the prepared pie plate. Bake for about 40 minutes, until the top has risen and cracked but the center is still slightly jiggly.

Step 6. Cool.

Remove from the oven and allow to cool at room temperature. Serve with whipped cream or a scoop of vanilla ice cream and hot fudge sauce.