To save time, start steps 1-3 of the frosting while baking and cooling the cupcakes. The strawberry purée should then be ready to use once the cupcakes have cooled and are ready for frosting.
Double Chocolate Cupcakes
Combine the cocoa powder and 3 ounces chopped bittersweet chocolate in a large bowl. Pour the coffee on top and whisk together until smooth. Refrigerate until no longer warm (about 20 minutes).
Meanwhile, preheat oven to 350ºF. Grease a standard 12-cup muffin tin or line with cupcakes liners.
In a medium bowl, whisk together the granulated sugar, bread flour, salt, and baking soda. Whisk in the chopped chocolate chips.
Add the vegetable oil, eggs, white vinegar, and vanilla extract to the cooled coffee mixture and whisk together until smooth. Add the dry ingredients to the wet and stir together gently just until evenly combined.
Divide the batter evenly between the prepared muffin cups – each will be about 3/4 full or slightly more. Bake in the preheated oven for 17-20 minutes, until a toothpick inserted into the center of one of the cupcakes comes out clean or with just a couple small crumbs.
Cool cupcakes in pan for 10 minutes, and then transfer to a wire rack to cool completely before frosting.
Strawberry Cream Cheese Frosting
Sprinkle the granulated sugar over the chopped strawberries in a bowl. Toss together and let sit for 1 hour to allow the sugar to pull out the juices from the strawberries.
Transfer the strawberry mixture to a blender and blend until smooth. Strain through a fine-mesh sieve into a small saucepan.
Bring strawberry mixture to a simmer over medium heat and simmer for about 15-20 minutes, stirring occasionally and reducing the heat as needed to maintain simmer. Once done, the mixture should have reduced substantially and be fairly thick. Allow to cool completely.
In the bowl of a stand mixer fitted with the whisk attachment (or using a bowl with a handheld electric mixer), cream together the butter and cooled strawberry purée until completely smooth, wiping down the bowl and beater as need. Add the cream cheese and continue to beat until smoothly incorporated, again wiping down bowl/beater as necessary.
Add the confectioner’s sugar in parts, beating in on low speed until incorporated and then increasing speed to whip frosting until smooth. Beat in the vanilla and salt.
Transfer the frosting to a piping bag fitted with a large closed star tip (I used Ateco 846). Starting at the center of each cupcake, pipe in a spiral out towards the edge to create a rose. Top cupcakes with a few pearl sprinkles if desired.
Store cupcakes in an airtight container. For short term storage (a few hours) they can be stored at room temperature, but for longer storage they should be kept in the refrigerator.