01 - Combine vanilla ice cream, whole milk, creamy peanut butter, and vanilla extract in a blender container.
02 - Blend on high speed for 30 to 45 seconds until completely smooth and creamy, pausing to scrape down sides of blender as needed.
03 - Test consistency and modify as desired: incorporate additional milk for thinner texture or add more ice cream for thicker body.
04 - Divide shake evenly between two chilled glasses, then top with whipped cream, crushed peanuts, and chocolate syrup if using. Serve immediately accompanied by straw and long-handled spoon.