For the Cupcakes:

1. Preheat the oven to 350 degrees F (180C). Prep cupcake pans with liners. I also recommend using baker’s spray. The papers will come right off the cakes.
2. Sift and whisk the dry ingredients together.
3. Cream butter and sugar together until well combined. Use a medium speed on your mixer so you are whipping in air without heating up the butter beyond room temperature. Stop the mixer and scrape down several times during this mix which will take at least 5 minutes. Don’t rush this step. The creaming process is the foundation for this style of baking.
4. When butter and sugar are adequately creamed, add in egg whites and vanilla. Scrape down the sides a couple of times and continue the mixer on medium. Do not crank her up full blast. Just. Don’t. Do. It.
5. Add in yogurt and mix until well combined.
6. You are left with the dry ingredients and the buttermilk. Finish it this way: Spoon in 1/3 of the dry ingredients and mix until it just starts to combine, then pour in half the buttermilk. The mixer should be on LOW. Scrape down the sides as needed. Spoon another 1/3 of the dry ingredients, mix until it starts to combine, and then pour in the rest of the buttermilk. When this is coming together, put in the remaining dry ingredients. Only mix on low until it just comes together. Do NOT overmix! We do not want gluten development as it will lead to a tougher cake, and we are going for tender. As Paul Hollywood would say, “This is cake not bread, so don’t over develop the gluten.” Actually I can’t remember a single instance where he actually said that, but you know he was thinking it, girl.
7. Gently whisk in the sprinkles. Pastel colors are better as bright ones tend to bleed their colors.
8. Fill cupcake liners 2/3s full and bake for 20 minutes + or – 2 or 3 minutes depending on your oven. When a toothpick comes out clean they are done. Don’t over bake! Allow them to cool completely on a wire rack for frosting.

For the Frosting:

1. Beat the room temperature butter for about 5 minutes on a medium speed. I have a video on making frosting, so please have a look at that.
2. Add the sifted icing sugar (powdered sugar) to the butter with the mixer turned off. Slowly crank up the speed on the mixer so the powdered sugar doesn’t wind up going everywhere. Add the sugar in a couple of additions, and scrape down your bowl before and after each addition! 
3. When the sugar is well incorporated, turn the mixer to medium high and add your flavoring. I used Lavender, but you can use whatever you prefer. Add the cream in a steady stream and monitor when the frosting is the perfect consistency. Kitchen temperature, mixer, humidity, etc all effect this, so don’t add it all if it isn’t needed. You want the buttercream to hold its shape, but not be so thick you can’t pipe it comfortably. It takes time to learn the proper consistency, so don’t be upset if your frosting is not perfect. It still tastes good! And if it’s too thick to pipe, use a spoon or offset spatula to frost your cupcakes.. Let’s be real, no home baker piped anything before Instagram.
4. At this point you can add a drop or two of gel paste food coloring. Use the gel paste as the liquid versions can impact the consistency of the frosting. Or don’t add anything. It’s completely up to you!
5. Put the frosting on the cupcakes. I piped mine using a swirl technique and then topped with more sprinkles.