In a large mixing bowl, combine the oil, sugar, maple syrup, non-dairy milk, and vanilla extract and mix until smooth. Sift in the flour, cocoa powder, black cocoa if using, baking soda, and salt. Mix to form a moist dough.

Make the filling: In another mixing bowl, beat together the peanut butter, confectioner's sugar, 2 tablespoons of non-dairy milk, and vanilla extract to form a moist but firm dough. If the filling is too dry (different natural peanut butters have different moisture levels), stir in the remaining tablespoon of non-dairy milk. If the dough is too wet, knead in a little extra powdered sugar.

Preheat oven to 350°F. Line a baking sheet with parchment paper.

Shape the cookies: Roll the peanut butter dough into 24 balls. Scoop a generous tablespoon of chocolate dough, flatten into a disc, and place a peanut butter ball in the center. Fold the sides of the chocolate dough up and around the peanut butter center and roll into a smooth ball between your palms. Place on a sheet of waxed paper and repeat with remaining dough. If desired, gently flatten cookies slightly, but this is not necessary.

Place dough balls on the lined baking sheet about 2 inches apart and bake for 10 minutes. Remove from the oven and let cookies cool on the sheet for 5 minutes before moving to a wire rack to cool completely. Store in a tightly covered container. If desired, warm cookies in the microwave for 10 to 12 seconds before serving.