In a mixing bowl cream together butter and sugars (both brown and cane) until light and fluffy, using a handheld electric whisk or a paddle attachment fitted in a stand mixer.
Add smooth peanut butter and mix until well combined.
Add milk and vanilla, mix to form creamy consistency.
Scrape down the sides with a spatula so that there are no lumps of butter.
Combine all the dry ingredients (flour, baking soda, baking powder, salt) in a separate bowl and add it to the butter mixture.
Mix on low speed to form cookie dough.
Cover with plastic wrap and allow the cookie dough to rest at room temperature for 30 minutes.
Preheat your oven to 350°F (175°C) and line a baking sheet with baking paper.
Use a 2-tablespoon cookie scoop or a measuring spoon to portion the dough approximately (40g for each cookie dough).
Roll the scooped cookie dough round by hand and toss it in cane or castor sugar.
Place them at least 2-3 inches apart on the baking sheet.
Bake for 10-12 minutes.
Use a round cookie cutter to re-shape the cookies in a perfect round shape while they’re straight out of the oven and warm.
Sprinkle sea salt If desired.