Prepare Oven & Dishes: Set your oven to preheat at 340°F (170°C / Gas Mark 3). Lightly grease four individual ramekins or oven-safe mugs.
Combine Dry Components: In a medium bowl, thoroughly mix the almond flour, sweetener, baking powder, cocoa powder, and instant espresso powder using a fork or whisk until uniform and free of clumps. If using, add the optional pinch of salt here.
Whisk Eggs: In a separate small bowl, beat the 3 large eggs vigorously with a whisk until they are pale and noticeably increased in volume.
Integrate Wet Ingredients: Pour the beaten eggs, melted butter (or coconut oil), peanut butter, and vanilla extract into the bowl containing the dry components.
Mix Batter: Gently fold and mix the wet and dry ingredients using a spatula or the whisk just until a smooth batter forms. Be careful not to overmix.
Portion and Top: Divide the batter evenly among the four prepared ramekins or mugs. Stud the top of each portion with the sugar-free chocolate chips.
Bake: Place the ramekins/mugs in the preheated oven. Bake for approximately 17 to 21 minutes. The cakes should be set around the edges but can remain slightly soft in the very center if desired. Check with a toothpick near the center for desired doneness.
Cool & Serve: Carefully remove the ramekins/mugs from the oven. Let them rest for 3-5 minutes to cool slightly and firm up before serving. Enjoy warm, optionally topped with low-carb ice cream, whipped cream, or an extra drizzle of peanut butter.