Preheat your oven to 350°F (177°C) and line two muffin trays with cupcake liners. This recipe yields around 16 to 18 cupcakes.

In a large mixing bowl, combine the vegetable oil, light brown sugar, eggs, and vanilla extract. You can either beat these ingredients together using an electric mixer or whisk them by hand until fully incorporated.

Add the peanut butter to the wet mixture, making sure it's smooth and free of brown sugar lumps.

In a separate bowl, whisk together the all-purpose flour, baking soda, and salt to ensure an even distribution of the leavening agent.

In a small measuring jug, gently whisk the milk and sour cream together using a fork.

Gradually incorporate half of the dry ingredients into the wet mixture, followed by half of the milk and sour cream mixture. Gently whisk by hand to combine, repeating the process with the remaining flour and milk mixture. Avoid over-mixing to keep the cupcakes light and fluffy.

Spoon the batter into the cupcake liners, filling each liner between 2/3 and 3/4 full. If you get only 12 cupcakes, the liners were filled too high.

Bake for 20-24 minutes, or until a toothpick inserted into the center of a cupcake comes out clean. Remove from the oven and allow the cupcakes to cool completely before frosting.

Using an electric mixer, beat the softened butter until it's light and fluffy. Then, blend in the peanut butter until the mixture is smooth and creamy.

Add the vanilla extract and 2 cups of the sifted powdered sugar. Start on low speed to prevent sugar clouds, and beat until smooth.

Gradually mix in the remaining powdered sugar, adding the cream or milk one tablespoon at a time. Continue until the frosting reaches your desired consistency and sweetness level.

Frost the cooled cupcakes using a knife or a piping bag fitted with a decorative tip. To finish, garnish with peanut butter candies for a fun and flavorful touch.