Ingredients for 1 servings:
1. 1/4 cup all-purpose flour (35 grams)
2. 1/4 teaspoon baking powder
3. 1/4 teaspoon salt
4. 8 ounces semisweet chocolate or 8 ounces bittersweet chocolate, chopped
5. 1/2 cup toasted and chopped walnuts or 1/2 cup pecans (50 grams)
6. 2 large eggs
7. 2 teaspoons pure vanilla extract (8 grams)
8. 1/3 cup sour cream (regular not low fat, 80 grams)
9. 1/2 cup unsalted butter (113 grams)
10. 3/4 cup granulated sugar (150 grams)

Directions:
1. Preheat oven to 300 degrees F (150 degrees C) and place rack in center of oven.
2. Prepare an 8 by 8 by 2 inch (20 x 20 x 5 cm) pan by lining the pan with a piece of aluminum foil, shiny side up.
3. Coat pan with room temperature butter, approximately 1 tablespoon (14 grams).
4. Can also line across the bottom and up 2 opposite sides with parchment paper.
5. In a bowl place the flour, baking powder, and salt and sift or whisk to combine.
6. Set aside.
7. Chop the chocolate in small pieces (can use a food processor) and set aside.
8. In a small bowl beat the eggs, vanilla, and sour cream just to mix; set aside.
9. In a medium sized saucepan, over medium heat, melt the butter.
10. Add the sugar and stir until sugar is partially melted.
11. Then add the chocolate and stir until the chocolate has melted.
12. Transfer to large mixing bowl.
13. Stir in egg mixture, then the sifted dry ingredients.
14. If the mixture is not perfectly smooth, beat it briefly with electric mixer (I use a hand mixer).
15. Stir in nuts, if using.
16. Pour into the baking pan and smooth top.
17. Bake for about 50- 55 minutes, until a toothpick inserted in the middle comes out almost (but not completely) clean.
18. Remove from oven and let stand at room temperature until cool.
19. Note: These are best chilled overnight.
20. Remove from pan by inverting on a cutting board and then re-inverting it onto a plate.
21. Chill brownies completely before cutting.
22. These freeze very well.