Prep the pan and oven: Heat the oven to 350°F (175°C). Line an 8x8-inch pan with parchment, leaving overhang for easy removal. Lightly grease the sides.

Melt chocolate and butter: In a heatproof bowl, melt 4 oz unsweetened chocolate with 1/2 cup (1 stick) butter. Use short microwave bursts or a double boiler. Stir until smooth and glossy. Let cool 3–4 minutes.

Whisk in sweetener: Add 3/4 to 1 cup granular erythritol sweetener (adjust to taste) to the warm chocolate mixture and whisk well. The warmth helps dissolve the granules for a smoother crumb.

Add eggs and flavorings: Whisk in 3 large eggs, one at a time, until the batter looks thick and shiny. Stir in 1 teaspoon vanilla, 1/2 teaspoon espresso powder (optional), and 1/4 teaspoon salt.

Combine dry ingredients: In a separate bowl, mix 1 cup finely ground almond flour, 1/3 cup cocoa powder, and 1/2 teaspoon baking powder. Break up any clumps with a fork or whisk.

Bring it together: Fold the dry ingredients into the wet until just combined. If using, fold in 1/3 cup sugar-free chocolate chips. The batter will be thick.

Spread and smooth: Scrape the batter into the prepared pan and smooth the top with a spatula. Sprinkle a pinch of flaky salt on top if you like.

Bake: Bake for 18–24 minutes, depending on your oven. Check at 18 minutes. A toothpick should come out with moist crumbs, not wet batter. Slightly underbaked is better for fudgy brownies.

Cool and set: Let brownies cool in the pan for at least 30–45 minutes. For the cleanest slices and maximum fudginess, chill for 1 hour before cutting.

Slice and serve: Lift out using the parchment overhang and cut into squares. Enjoy as is, or warm gently and top with whipped cream.