Line a baking sheet with parchment paper or wax paper, then arrange 20 shortbread cookies in a single layer.

Place the caramel bits and heavy cream in a microwave-safe bowl. Microwave in 20–30-second intervals, stirring between each interval, until completely smooth; this generally takes about 1–2 minutes total.

Spoon approximately 1 tablespoon of melted caramel onto each shortbread cookie. Gently spread the caramel if needed, then refrigerate the cookies for about 20 minutes, or until the caramel is firm.

Melt the milk chocolate chips in a microwave-safe bowl using 20–30-second intervals and frequent stirring. Stop heating when only a few chips remain unmelted, then stir until the residual heat makes the chocolate smooth.

Dip each chilled, caramel-topped cookie into the melted chocolate, or spoon the chocolate over the tops. Return the coated cookies to the lined baking sheet.

Sprinkle with flaky sea salt if desired before the chocolate sets. Refrigerate for another 15–20 minutes, until the chocolate is firm.