Preheat the oven to 350 degrees F. Butter and flour 3 (9-inch) cake pans. Cut 3 circles of waxed or parchment paper to fit the bottoms of the pans, then press them in. In a mixer fitted with a whisk attachment (or using a hand mixer,) cream the butter until smooth. Add the sugar and eggs and mix until fluffy, about 3 minutes. Add the vanilla, cocoa, baking soda and salt; mix. Add half of the flour, then half of the sour cream, and mix. Repeat with the remaining flour and sour cream. Drizzle in the hot coffee and mix until smooth. The batter will be thin.
Pour into the prepared pans and bake until the tops are firm to the touch and a toothpick inserted into the center comes out clean (a few crumbs are okay) about 35 minutes. Halfway through the baking, quickly rotate the pans in the oven to ensure even baking, but otherwise try not to open the oven. Let cool in the pan 10 minutes. Turn out onto wire racks and let cool completely before frosting.
To frost the cake, use a spatula to cover 2 of the cake layers with frosting. Stack them together. Flip the third cake layer over and rest it on the top to create a very flat top for the cake. Frost on the sides and top with a thin "crumb" layer to seal all the crumbs in and chill. Repeat with a finishing layer of butter cream. Place about 2 cups of butter cream in a potato ricer and press it through onto the top of the cake moving it in a circular motion to look like spaghetti. Place chocolate truffle meatballs around on top and chill until ready to serve. Just before serving, pour on the strawberry puree.
In a saucepan place the sugar and carefully pour the water around the edge. Using your finger make an X in the pan to help the water gently mix with the sugar. Bring to a boil and cook to softball stage (235 degrees F.) Meanwhile, whip the egg whites in a mixer with a whip attachment until light and fluffy. When sugar is softball slowly pour it into the bowl down the side and continue whipping, adding vanilla, until incorporated and then cooled. Add the butter 1 cube at a time while whipping until it is a thick butter cream (check flavor and consistency of butter cream before continuing to add butter, as not all of the 2 cups may be needed). Keep at room temperature while frosting the cake.
Heat the heavy cream in a small saucepan, and as soon as it boils, turn off the heat. Meanwhile, put the chopped bittersweet chocolate in a medium bowl. Pour the hot cream into the bowl. Whisk until the chocolate is melted and the mixture is smooth, add the peanut butter and whisk until smooth. Cover and let rest in a cool place overnight--do not refrigerate. The mixture will become firm but not hard.
The next day, scoop balls of truffle mixture using an ice cream scoop onto baking sheets lined with parchment paper. Refrigerate until set, about 1 hour. Use your palm to gently press down the point that sticks up on each truffle. Transfer to the freezer and freeze until hard, 2 to 3 hours or overnight.
Melt the semisweet chocolate in the top of a double boiler set over barely simmering water. It should be liquid, but not so hot that you can't touch it. Spread the cocoa powder out on a sheet pan with sides.
Working in 2 batches to avoid crowding the pan of cocoa, dip the frozen truffles one at a time into the melted chocolate, shaking off any excess. Set coated truffle on the cocoa. Gently but thoroughly shake pan containing the truffles and the cocoa after the chocolate has started to set until truffles are completely coated. Carefully remove to another pan and refrigerate, uncovered for 30 minutes. Transfer to an airtight container and keep chilled.
In a blender, puree the strawberries and add a teaspoon of water if necessary to adjust consistency to a thick, but not pasty consistency. Adjust sweetness to taste with sugar.