Melt 1/2 cup (8 Tbsp; 113g) butter in a large bowl and set aside to slightly cool as you prepare the rest of the batter.

Using a handheld or stand mixer fitted with a whisk attachment, beat the eggs and sugar together on high speed for 8–10 minutes. The mixture should be thick, pale, and form ribbons when you lift the beater(s). Beat in the vanilla and peppermint extract just until combined.

Sift the flour, cocoa powder, baking powder, salt, and espresso powder (if using) together into the bowl with the eggs. Using a silicone spatula, gently fold until just combined.

Pour in the melted butter and fold with a spatula to combine. It will take a minute of folding to fully incorporate. The batter will be glossy.

Cover the batter and refrigerate it for at least 45 minutes and up to 2 hours. Any longer and the butter will firm up too much, leaving the batter heavy and the madeleines dense.

Preheat the oven to 425°F (218°C).

Melt the remaining 2 Tbsp (28g) of butter. Lightly brush the wells of the madeleine pan with melted butter.

The batter will be thick, airy, and spongey after resting. Do not stir it—we don’t want to deflate it. Spoon 1 Tablespoon of batter into the center of each scalloped well. No need to spread it to the edges. Just plop it in the center. (Cover and refrigerate remaining batter if you do not have 2 madeleine pans to bake the batter all at once.)

Bake for 3 minutes at 425°F; then, without opening the oven, reduce the temperature to 350°F (177°C) and bake for 6-7 more minutes. To test for doneness, lightly press on the top of a madeleine. If it springs back, they’re done. If your finger leaves an indent, let them bake for another minute and then test again.

Cool the madeleines in the pan for 5 minutes, and then invert the pan onto the cooling rack. Let the madeleines cool completely.

Place the chopped chocolate in a heatproof bowl or 2-cup liquid measuring cup (best for dunking!). Microwave in 20-second increments, stirring after every 20 seconds until completely melted and smooth. (Or you can use a double boiler.) Dip the tops of the cooled madeleines in the melted chocolate and place them on a baking sheet lined with parchment paper. Sprinkle crushed candy canes on top while the chocolate is still wet. Let chocolate set at room temperature, or speed it up by placing the baking sheet in the refrigerator.

Chocolate madeleines are best the day or day after they’re made. They’ll lose a lot of moisture over time, which noticeably affects the texture, so I suggest baking and enjoying them fresh. For this reason, I don’t recommend freezing them, either.