Line a baking sheet with parchment paper or a silicone baking mat to prevent sticking and make cleanup easier.

In a large mixing bowl, combine the softened butter and creamy peanut butter. Using a hand mixer or stand mixer on medium speed, beat until smooth and creamy, about 1–2 minutes. Scrape down the sides of the bowl as needed.

Add the vanilla extract and fine sea salt. Gradually add the powdered sugar, mixing on low speed at first to avoid a sugar cloud. Once mostly incorporated, increase to medium speed and mix until the mixture is thick and slightly stiff, similar to cookie dough.

Gently fold in the finely crushed Butterfinger candies with a spatula or wooden spoon until evenly distributed. Do not overmix; you want distinct crunchy bits throughout. The mixture should be firm enough to roll without sticking excessively to your hands.

If the mixture feels too soft or warm, refrigerate the bowl for 15–20 minutes. This will make rolling easier and help the balls hold their shape.

Using a small cookie scoop or a spoon, portion about 1 tablespoon of mixture per ball. Roll each portion between your palms until smooth and place on the prepared baking sheet. You should end up with about 24–28 balls, depending on size.

Transfer the baking sheet to the freezer for 20–30 minutes, or to the refrigerator for about 45 minutes, until the centers are firm to the touch. Cold centers are much easier to dip in warm chocolate.

Place the semi-sweet chocolate chips and coconut oil or shortening (if using) in a microwave-safe bowl. Microwave in 20–30 second bursts, stirring well after each, until the chocolate is smooth and fully melted. Alternatively, melt the chocolate in a heatproof bowl set over a pot of gently simmering water. The chocolate should be fluid but not scorching hot.

Working with a few chilled balls at a time, drop one ball into the melted chocolate. Use a fork to gently roll it until coated, then lift it out, allowing excess chocolate to drip back into the bowl. Tap the fork lightly on the edge of the bowl for a thinner coating, then slide the coated ball back onto the parchment-lined baking sheet.

While the chocolate coating is still soft, immediately sprinkle the tops with extra crushed Butterfinger, sea salt flakes, or festive sprinkles. Work fairly quickly so the toppings adhere before the chocolate sets.

Return the baking sheet to the refrigerator for 20–30 minutes, or until the chocolate coating is fully set and firm.

Once the chocolate is set, enjoy the Butterfinger balls right away or transfer them to an airtight container. Keep refrigerated until serving.