Preheat the oven to 350F and grease and line an 8x3 inch or two 8x2 inch baking pans.

In a large bowl, whisk together the flour, cocoa powder, baking powder and salt until evenly distributed.

In a separate bowl, whisk the sugar, oil, eggs, and sour cream until well combined.

Sift the dry ingredients over the wet ingredients and whisk together about halfway.

Pour in the hot coffee and whisk until the batter is smooth.

Scrape the edge of the bowl and give it a good mix. Pour into prepared cake tin(s).

Bake for about 40 minutes until the center springs back when pressed.

Let the cake rest for 10 minutes in the pan, then flip onto a tea towel to cool for 30 minutes.

Once cooled, slice the cake in half.

Mix the espresso, honey, and cinnamon until well combined. Let cool and brush half of the syrup onto the sliced side of each cake.

Beat the cold mascarpone with the powdered sugar until smooth.

Add the vanilla bean paste and beat at medium speed.

Stream in the cold heavy whipping cream in increments, scraping the bowl each time.

Once all cream is added, increase speed to full until it thickens and holds peaks.

Add the pistachio butter and mix just until combined.

Add the salt and vanilla, mix to combine.

Spread half of the cream on the first layer of cake, drizzle with pistachio butter, then repeat with the top layer.