In a large mixing bowl, beat the peanut butter and softened butter together with a hand mixer or stand mixer on medium speed until smooth and creamy, 1–2 minutes, with no streaks of butter remaining.

Beat in the vanilla extract and fine sea salt until combined. Taste a small amount and adjust the salt if needed for a sweet-salty balance.

With the mixer on low speed, add the powdered sugar 1 cup at a time. After 3 cups, check the texture: the dough should be thick, soft, and pull away from the sides of the bowl. If it is still sticky, add up to 1/2 cup more, a little at a time, until it holds a ball shape without sagging.

Cover the bowl and chill the peanut butter mixture for 20–30 minutes to firm it up and make rolling easier.

Line a baking sheet with parchment or wax paper. Scoop about 1 tablespoon of the peanut butter mixture for each ball and roll between your palms until smooth and round. Place on the lined tray. You should get about 36–40 balls.

Refrigerate the rolled balls for at least 1 hour, or freeze for 20–30 minutes, until firm enough to stay on a toothpick or fork without sliding.

In a microwave-safe bowl, combine the chocolate chips and shortening or coconut oil. Microwave in 20–30 second bursts, stirring well after each, until the chocolate is smooth and fully melted. Alternatively, melt in a heatproof bowl over a pot of barely simmering water.

Remove a few peanut butter balls from the refrigerator at a time, keeping the rest cold. Insert a toothpick into the top of each ball to use as a handle for dipping, or place a ball on a fork and use a spoon to pour chocolate over it.

Dip each ball into the melted chocolate, leaving the top center uncovered so it resembles a buckeye. Let excess chocolate drip off, then place the ball back on the parchment-lined tray. Repeat with remaining balls, reheating the chocolate briefly if it thickens.

When the chocolate has started to set but is not fully hardened, gently smooth over any toothpick holes on top with a clean fingertip or the back of a small spoon.

Refrigerate the tray for about 30 minutes, or until the chocolate coating is firm. Transfer the buckeye balls to an airtight container, layering with parchment paper so they don’t stick together.

If desired, before the chocolate fully sets, sprinkle some buckeyes with flaky sea salt, holiday sprinkles, or crushed peanuts. Serve chilled or at cool room temperature.