In a large bowl, use a hand mixer or sturdy spatula to mix the peanut butter, softened butter, salt, and vanilla until well blended. Gradually stir in the powdered sugar until the mixture is smooth.
Cover the bowl and refrigerate for 15 minutes to firm up. The mixture should be scoopable but not sticky.
Using clean hands or a small cookie scoop, form the dough into 1-inch balls (you should get 20 to 24 total). Roll between your palms for a smooth finish, if you like.
Place them on a parchment-lined baking sheet and chill in the refrigerator for 20 minutes so they hold their shape.
In a microwave-safe bowl, melt the chocolate chips and 1 teaspoon vegetable oil in 20- to 30-second intervals, stirring between each, until smooth and glossy. If the mixture seems too thick for dipping, stir in up to 1 additional teaspoon of oil, a little at a time, until it's dippable.
Working with a few at a time, use a fork or dipping tool to lower each chilled ball into the melted chocolate, turning to coat evenly. Let the excess chocolate drip back into the bowl, then return the coated balls to the parchment-lined baking sheet.
Refrigerate until the chocolate is fully set, about 20-30 minutes.
Serve immediately or cover and refrigerate.