Preheat oven to 350°F (175°C). Line a small baking sheet with parchment.
In a small bowl, stir peanut butter and coconut sugar until smooth and thick.
Add flour, baking powder, and salt, and stir again.
Add the milk and vanilla and mix until a soft, cohesive dough forms.
Roll the dough into a ball, set it on the parchment, and gently press it flat with a fork in a crisscross pattern to about 2½ inches wide. Add fork marks in the middle.
Bake for 15-20 minutes, until the edges look set. The center will still look soft.
Cool on the pan for at least 5 minutes so it firms up before you move it.
Notes
Please note that the nutrition data given here is a ballpark figure. Exact data is not possible.