Eclipse Cupcakes are fun and easy cupcakes, decorated to look like the stages of the solar eclipse! They're simple enough for kids to help with, and are perfect for eclipse viewing parties! The appeal of these cupcakes is definitely the decorations, so don’t hesitate to use a store-bought cupcake mix if you’d like. I do recommend a homemade frosting, if possible, since that will give a nice smooth top to the cupcakes, but in a pinch, canned frosting will work too!
Preheat the oven to 350 F. Line cupcake pans with 24 paper wrappers.
Add the butter and both sugars to the bowl of a large stand mixer fitted with a paddle attachment. Beat them together on medium-high speed, until light and fluffy, about 5 minutes. Add the eggs one at a time, beating well after each addition. Add the vanilla extract and mix it in.
In a separate bowl, whisk together the buttermilk, sour cream, and water (or coffee, if using). In a different bowl, sift together the flour, cocoa powder, baking soda, and salt. With the mixer running on low, add a quarter of the sifted flour mixture. When the flour streaks have almost all disappeared, add a third of the liquid to the mixing bowl. When that’s incorporated, continue to add the drys and wets in an alternating pattern, ending with the dry ingredients.
When the dry ingredients are nearly incorporated, stop the mixer. Scrape down the bottom and sides of the bowl with a rubber spatula, and finish mixing the cake by hand. Scoop the batter into the cupcake pans. Bake for 20-22 minutes, until the tops spring back when lightly pressed. Cool completely before decorating.
To Make the Buttercream:
Combine the whites, powdered sugar, and salt in the bowl of a large stand mixer fitted with a paddle attachment. Mix everything together on low speed, until the sugar is moistened and no dry patches remain. Turn off the mixer, scrape down the sides and bottom of the bowl with a spatula, then turn the mixer to medium speed. Beat on medium for 5 minutes.
After 5 minutes, turn the mixer to medium-low and start adding the softened room temperature butter, 1-2 tablespoons at a time. Once all of the butter is incorporated, add the vanilla extract and mix it in. Stop the mixer and scrape down the bottom and sides once more. Turn the speed to medium and beat the buttercream for 10 minutes. At the end, you’ll have a frosting with a wonderfully light and creamy texture. Add the yellow food coloring to get a deep yellow color.
The frosting can be used right away, or stored in the refrigerator for up to two weeks, or the freezer for up to two months. If you have chilled the frosting, let it come to room temperature and then beat it for several minutes to smooth it out and restore its texture before using it.
Place the yellow frosting in a piping bag fitted with a coupler. Hold the bag perpendicular to the top of a cupcake, about 1 inch above the surface. Squeeze the bag until the frosting comes out and starts forming a round blob on top of the cupcake. Continue to apply even pressure, making the blob grow bigger, until it almost reaches the edges of the cupcake.
Place a metal spatula in a pitcher of very hot water, to heat the metal, and dry it off so it’s hot but not wet. Press the spatula on top of the buttercream and gently slide it back and forth, using even pressure, so that you flatten out the top of the frosting, creating a round and completely flat frosting surface. Repeat with all of the cupcakes.
Put on plastic gloves (optional but highly recommended!) and spray the edges of each cupcake with orange color mist—this will give them a nice airbrushed effect and make them look more like a sun.
Sprinkle your work surface with cocoa powder, and roll out the fondant into several long, thin strips, each about 2.5-3 inches wide.
Use a round cutter to cut out circles from the fondant that are about the same size as the frosting circles on top of the cupcakes. Keep one circle whole, to be the full eclipse, and for the rest of the circles, use the cutter to trim off different amounts of the edges, so that you’re left with ovals of varying sizes, ranging from very small to very large. Make sure you make 2 of each size, to represent both the waxing and waning eclipse. Since this makes 24 cupcakes, you can either make one looooong set of eclipse cupcakes, or do 2 or 3 smaller sets showing fewer stages of the eclipse—it’s up to you!
After all the fondant pieces are cut out, gently place them on the cupcakes. For the best taste and texture, serve these cupcakes at room temperature.