Preheat oven to 325℉ (160℃) | 140℃ Fan Convection. Prepare three 6-inch cake pans with a light coating of baking oil spray and line the bottoms with parchment paper.
Rye Chocolate Coffee Cake
In a medium bowl, whisk together granulated sugar, brown sugar, eggs, oil, and vanilla until smooth and velvety.
133 grams granulated sugar, 67 grams dark or light brown sugar, 2 large eggs, 120 grams/ml sunflower seed oil or neutral oil, 2 teaspoons vanilla bean paste or pure vanilla extract
Whisk together the all purpose flour, rye flour, cocoa powder, *optional espresso powder, baking powder, baking soda, and salt in a large bowl.
Pour the wet ingredients into the flour mixture. Using a silicone spatula stir the wet ingredients into the flour mixture to create a thick paste like consistency.
Switch back to the whisk and pour in the hot coffee. Stir slowly to mix in the coffee and thin the batter until smooth.
120 grams/ml strong brewed coffee
Add in the sour cream and whisk until there are no more white streaks.
120 grams sour cream
Divide the batter evenly between the three pans. Weigh the batter to be exact for even cake layers.
Bake the cake layers on the middle oven rack for 35-38 minutes. Cakes are baked when the sides pull away from the pan, a toothpick inserted into the center comes out clean and the cake springs back when gently pressed with finger tip. *Check cakes at the 30-minute mark as all ovens bake differently.
Place cake pans on wire rack to cool for 15 minutes before removing and placing cake layers directly onto wire rack to cool completely.
Chocolate Cream Cheese Frosting
In a large bowl beat softened butter and cream cheese together until smooth with a handheld electric mixer.
113 grams unsalted butter, 113 grams full fat cream cheese
Add the honey, vanilla, and half the powdered sugar. Mix on low speed until smooth.
1 teaspoon honey, 1 teaspoon vanilla bean paste or pure vanilla extract
Mix in the cocoa powder, espresso powder, and remaining powdered sugar until smooth. Scrape sides and bottom of the bowl with a spatula as needed to make sure everything is well mixed.