Line a baking sheet or tray with parchment paper or wax paper. For easier dipping, chill the doughnut holes for about 10 minutes so they are firmer and less likely to tear or shed crumbs.

Place the chocolate chips or melting wafers in a microwave-safe bowl. Microwave in 20–30-second intervals, stirring thoroughly after each interval, until smooth; stir in the optional shortening or coconut oil if the chocolate seems too thick.

Dip the rounded top or one half of each mini doughnut hole into the melted chocolate. Let excess chocolate drip back into the bowl while keeping the coating fairly thick enough to hold the nut or sprinkle topping.

Immediately roll or sprinkle the chocolate-coated portion with finely chopped peanuts, pecans, or chocolate sprinkles. Set the decorated doughnut hole on the lined tray and insert a 1/2-inch pretzel piece into the top as the acorn stem.

Repeat with the remaining doughnut holes, warming the chocolate briefly only if it becomes difficult to spread. Refrigerate the tray for 15–20 minutes, or until the chocolate is firm, then serve the acorn doughnuts at room temperature.