- Prep Time: 30h
- Cook Time: 45h
- Total Time: 1h 15m
- 1 lb Unsalted butter (4 sticks)
- 1 lb Plus 12 oz. Bittersweet (or semisweet) chocolate chips, divided
- 6 oz Unsweetened chocolate
- 6 Eggs, Extra-large (or 7 large eggs)
- 1 tbsp. Instant espresso powder
- 2 tbsp. Vanilla extract
- 2 1/4 c Sugar
- 1 tbsp. Baking powder
- 1 tsp. Kosher salt
- 3 c Roasted walnuts or pecans, diced (optional)
- 1 1/4 c AP flour, divided into 1 c and 1/4 c
- Butter and flour 13x18 sheet pan, or 2 - 13x9 pans. Preheat oven to 350F.
- In a double boiler, or a bowl placed over a pan of simmering water, melt together the butter, 1 lb chocolate chips, and unsweetened chocolate. Cool slightly. In a large bowl, stir together eggs, espresso, vanilla and sugar. Stir in chocolate mixture and cool to room temperature.
- Whisk together 1 c flour, baking powder and salt. Add to bowl containing chocolate mixture. Mix together remaining chocolate chips, nuts (if using) and 1/4 c flour. Then fold into batter. Pour into prepared pan.
- Bake until tester just comes out clean, being careful to not overbake. This takes about 28-30 minutes. Best to underbake rather than ovebake. Cool thoroughly, refrigerate well, then cut into squares.