Line a mini muffin tin with paper liners or prepare a baking sheet with parchment paper.
Gently melt the chocolate over a double boiler or in short bursts in the microwave, stirring until smooth and glossy, about 2 minutes.
Spoon about 1 teaspoon of melted chocolate into each cup, then gently tap the tin to level the chocolate and remove air bubbles.
Place the filled tin in the freezer for 5-10 minutes until the chocolate is just firm and set.
In a small bowl, stir the peanut butter with a pinch of salt and the honey or maple syrup until smooth and creamy.
Spoon about a teaspoon of the peanut butter mixture onto each chocolate layer, spreading slightly if needed.
Cover the peanut butter layer with the remaining melted chocolate, smoothing the top with a spatula.
Sprinkle a tiny pinch of flaky sea salt on top of each cup, if desired, then chill in the refrigerator or freezer for another 20-30 minutes until fully set and glossy.
Once cooled and firm, remove the peanut butter cups from the tin or peel away the paper liners, and let sit at room temperature for a few minutes before serving.