Preheat oven to 400°F (200°C). Butter 20 to 22 muffin pan wells, or butter a 12x8½-inch rimmed baking sheet.
In a medium bowl, whisk together flour, cocoa, cinnamon, baking soda, baking powder, cloves, salt, nutmeg, and ginger (if using).
In the bowl of a stand mixer fitted with paddle attachment, beat eggs at high speed until very foamy and pale yellow. Add milk, muscovado sugar, honey, butter, and vanilla. Add flour mixture, and beat at medium-low speed until well combined. Spoon batter into prepared wells or prepared baking sheet.
Bake until a wooden pick inserted in center comes out clean, 15 to 20 minutes for muffin pans or 20 to 25 minutes for baking sheet. Let cool completely in pans.
Line a rimmed baking sheet with plastic wrap; place a wire rack on top. Line a baking sheet with parchment paper.
If using muffin pans, slice each cake in half horizontally. Spread 2 tablespoons dulce de leche on bottom half of cakes, and cover with top half of cakes. Place on prepared wire rack.
If using a baking sheet, using a 3-inch round cutter, cut cake. Spread 2 tablespoons dulce de leche on top of half of cakes, and place remaining cakes on top. Place on prepared wire rack.
Pour melted chocolate over cakes until fully covered. (Reuse chocolate collected on baking sheet, if necessary.) Place cakes on parchment-lined pan, and let stand until chocolate is set. Drizzle with remaining dulce de leche.