Instructions

for the cake

Adjust oven rack to middle position and heat oven to 350 degrees. Grease two 9-inch round cake pans, line with parchment paper, grease parchment, and flour pans. Whisk flour, baking soda, baking powder, and salt together in bowl. In second bowl, whisk boiling water, chocolate, cocoa, and espresso powder until smooth.
Using stand mixer fitted with paddle, beat butter and sugar on medium-high speed until pale and fluffy, about 3 minutes. Add eggs, one at a time, and beat until combined. Add sour cream and vanilla and beat until incorporated.
Reduce speed to low and add flour mixture in 3 additions, alternating with chocolate mixture in 2 additions, scraping down bowl as needed. Give batter final stir by hand.
Divide batter evenly between prepared pans and smooth tops with rubber spatula. Bake until toothpick inserted in center comes out clean, 25 to 30 minutes, rotating pans halfway through baking.
Let cakes cool in pans on wire rack for 10 minutes. Remove cakes from pans, discarding parchment, and let cool completely on rack, about 2 hours.

for the topping

Meanwhile, reserve 1 whole strawberry. Halve remaining 19 strawberries. Place jam and water in large bowl and microwave until bubbling, about 2 minutes. Add whole and halved strawberries to jam mixture and toss until evenly coated. Transfer strawberries to parchment-lined baking sheet and spread into single layer. Set aside.

for the frosting

Strain strawberries through fine-mesh strainer, pressing firmly on fruit with rubber spatula (discard juice). Transfer strawberry solids to food processor and process until smooth, about 1 minute.
Using stand mixer fitted with whisk attachment, whip butter on medium-high speed until smooth, about 20 seconds. Add sugar and whip on medium-low speed until most of sugar is moistened, about 45 seconds. Scrape down bowl. Add vanilla, salt, and strawberry puree and whip on medium-high speed until light and fluffy, about 4 minutes, scraping down bowl as needed.
Place 1 cake layer on plate or pedestal. Spread 1½ cups frosting evenly over top, right to edge of cake. Top with second cake layer, pressing lightly to adhere. Spread remaining frosting evenly over top and sides of cake.
Place whole glazed strawberry in center of cake. Arrange 5 glazed strawberry halves, stem end down and cut side facing in, around whole strawberry. Repeat in concentric circular pattern 2 times, angling tips of strawberries outward at 45 degrees and alternating orientation of cut side and round side of strawberries. Arrange remaining strawberry halves in circle, cut side down, at base of subsequent rings of strawberries, with points facing outward. Serve.