Step 1

Place a rack in middle of oven and preheat to 400°. If using raw sweet potatoes, wrap in foil and roast on a parchment-lined baking sheet until tender (a knife should slide easily into flesh), 50–60 minutes.

Step 2

Unwrap sweet potatoes and let sit until cool enough to handle. Transfer to a small bowl. Using a potato masher or fork, smash until smooth. Measure out 1¼ cups (250 g) purée; save any extra for another use.

Step 3

Reduce oven temperature to 325°. Butter a 9x5" loaf pan or lightly coat with nonstick spray. Line pan with parchment paper, leaving overhang on long sides. Whisk flour, salt, baking powder, baking soda, cinnamon, nutmeg, and cloves in a medium bowl.

Step 4

Whisk mashed sweet potato (homemade or canned), eggs, granulated sugar, zest, and vanilla extract in a large bowl until smooth. Gradually add oil, whisking constantly until completely incorporated. Using a rubber spatula, fold in dry ingredients in 2 batches, mixing just until combined after each addition. Scrape batter into prepared pan and smooth surface with an offset spatula.

Step 5

Bake cake until golden and a tester inserted into the center comes out clean, 75–90 minutes. Transfer cake to a wire rack and let cool in pan 15 minutes. Using parchment overhang, lift cake out of pan and onto rack. Remove parchment and let cake cool completely.

Step 6

Bring cream, butter, sugar, coffee, and salt to a simmer in a small saucepan over medium heat. Remove from heat, add chocolate and vanilla, and whisk until chocolate is melted and mixture is smooth. Let cool until thickened slightly, 40–60 minutes.

Step 7

Pour ganache over cake (it should flow over the sides) and, using a small offset spatula, smooth it evenly over surface. Chill cake until ganache is set, 20–30 minutes. Bring cake to room temperature before serving.Do ahead: Unglazed cake can be baked 3 days ahead. Store tightly wrapped at room temperature.