Combine peanut butter, sugar and butter in small bowl until well blended. If mixture is very soft, mix in an additional tablespoon of sugar. Shape peanut butter mixture into 30 1/2- to 3/4-inch balls flattening slightly.
Melt morsels and shortening in medium, uncovered, microwave-safe bowl on MEDIUM-HIGH (70%) power for 1 minute; stir. Morsels may retain some of their shape. If necessary, microwave at additional 10- to 15-second intervals, stirring just until melted. Spoon 1 measuring teaspoon of melted morsels into each cup. Place peanut butter filling onto top of melted morsels. Top each with a measuring half teaspoon of melted morsels. Sprinkle with a few grains of sea salt. Refrigerate for 20 minutes or until firm. Store in covered container in refrigerator.