Preheat your oven to 180°C (350°F) and line a muffin tin with paper liners.
In a large bowl, whisk together the chunky peanut butter, brown sugar, and eggs until the mixture is smooth and fragrant, about 2 minutes. The batter will turn slightly glossy and creamy.
In a separate bowl, sift together the all-purpose flour, baking soda, and salt to ensure even distribution and a light texture.
Gradually add the dry ingredients to the wet mixture, folding gently with a spatula until just combined. Be careful not to overmix; the batter should be slightly lumpy but cohesive.
Spoon the batter into the prepared muffin tin, filling each cup about three-quarters full. The batter will be thick but scoopable.
Bake in the preheated oven for 15 to 18 minutes, until the muffins are golden around the edges and a toothpick inserted into the center comes out clean. The aroma will be warm and nutty.
Remove the muffins from the oven and let them cool in the tin for about 5 minutes. Then transfer them to a cooling rack to cool completely, allowing the crumb to set and develop its moist, tender texture.
Once cooled, enjoy these cozy, slightly messy muffins with a glass of milk or a cup of coffee. They’re best eaten within a day or two for optimal freshness.