2/3 cup marzipan
1 tablespoon unsweetened cocoa powder
Make about 10 mushroom stems by rolling dime- to quarter-size pieces of marzipan
into cylinders. Make large and small mushroom caps by rolling dime- to
quarter-size pieces of marzipan into balls; then pinch into cap shape. Attach
stems, pressing gently. Dust with cocoa.
Bring milk to boil in medium
saucepan over medium heat. Whisk yolks and sugar in small bowl until well
blended; whisk in flour. Whisk hot milk into egg mixture. Return to same
saucepan. Whisk over medium heat until custard thickens and boils, about 1 1/2
minutes. Transfer to processor; cool to room temperature, about 1 hour. Add
marzipan; process until smooth, about 1 minute. Blend in butter 1 piece at a
time, then both extracts. Cover and refrigerate filling at least 4 hours or up
to 2 days.
Preheat oven to 350°F. Butter a 15
x 10 x 2-inch sheet pan. Line bottom with parchment paper; butter and flour
parchment. Whisk eggs, 3/4 cup sugar, vanilla and salt in large metal bowl. Set
bowl over pot of simmering water. Whisk until just warm, about 2 minutes. Remove
bowl from over water. Using electric mixer, beat mixture until tripled in
volume, about 6 minutes. Sift flour over; fold in until just combined. Gently
fold in butter (do not overmix, or batter will deflate). Spread batter in
prepared pan. Bake until tester inserted into center comes out clean, about 20
minutes. Sift powdered sugar over towel. Run knife around edge of pan to loosen
cake. Turn hot cake out onto towel. Peel off parchment. Starting at 1 long side
and using towel as aid, gently roll up cake jelly-roll style. Cool. Unroll cake.
Spread filling over. Re-roll cake; place cake, seam side down, on platter.
Refrigerate cake while preparing frosting.
Bring cream and butter to boil in medium
saucepan over medium-high heat, stirring to melt butter. Remove from heat.
Add both chocolates; whisk until melted. Transfer to medium bowl. Let cool at
room temperature until thick enough to spread, about 1 hour.
Starting 1 inch in from each end of cake, cut on diagonal to remove one
3-inch-long piece of cake from each end. Attach 1 cake piece at sides of cake
near each end. Spread frosting over top and sides of cake and pieces. Using
tines of fork, draw concentric circles on cake ends to resemble tree rings. Draw
fork along length of cake to form bark design. Garnish with Marzipan Mushrooms.