Preheat your oven to 180°C (350°F) and line a muffin tin with paper liners or grease it well.
In a large mixing bowl, whisk together the sifted flour, sugar, baking powder, baking soda, and salt until combined and light in color.
In a separate bowl, stir together the peanut butter, milk, vegetable oil, and eggs until the mixture is smooth and slightly frothy, with a fragrant aroma of peanut butter filling the air.
Pour the wet mixture into the dry ingredients and gently fold together with a spatula until just combined, taking care not to overmix — the batter should be slightly lumpy but uniform.
Divide the batter evenly among the muffin cups, filling each about two-thirds full, and optionally sprinkle with chocolate chips or a pinch of sea salt for extra flavor.
Bake in the preheated oven for 15-20 minutes, until the muffins turn a golden brown and a toothpick inserted into the center comes out clean with a slight crumbly texture.
Remove the muffins from the oven and let them cool in the tin for about 5 minutes, allowing the steam to settle and the crumb to firm up slightly.
Transfer the muffins to a wire rack to cool completely or serve warm for a soft, tender crumb with a nutty aroma that fills the room.