Line a 6-cup muffin/cupcake pan with paper or parchment liners. Measure out all ingredients and bring butter, milk, and egg white to room temp.
Add softened butter to a medium bowl and whip until creamy. Next add sugar and mash into the butter with a fork to prevent the ingredients from flying when mixed. Using a handheld electric mixer, cream together butter and sugar until light and fluffy, 1-2 minutes.
Add egg white and vanilla. Beat on medium until smooth.
Add half the flour (¼ cup) to the mixing bowl along with baking soda and salt. Mix on low until incorporated.
Mix in milk on low. Add remaining ¼ cup of flour and mix on medium until well-mixed and smooth.
Divide batter between prepared cupcake cups, filling just under 2/3 full. This should make exactly 6 cupcakes. Bake for 17-19 minutes, until a toothpick inserted into the center of the cupcakes comes out clean or with just a few dry crumbs.
Once cool enough to handle, transfer to cupcakes a wire cooling to cool completely before frosting.
While the cupcakes cool, make the frosting.
Frosting Instructions
In a large mixing bowl using a handheld mixer or in the bowl of a stand mixer fitted with the paddle attachment, beat the butter until smooth and creamy, stopping to scrape down sides as needed. Add the powdered sugar and mix on low speed at first to incorporate, then increase to medium speed and continue mixing for 1-2 minutes or until fully combined. Add the heavy cream, vanilla extract, and salt and continue mixing on medium speed until everything is well combined.
Divide and dye frosting desired colors with gel food coloring and transfer to a piping bag with your choice of tip for decorating. I used an open star tip for the succulents and closed star tip for the frosting rose. Frost cupcakes once cooled completely. Add sprinkles if you'd like and have fun with it!
Notes
This is enough frosting to frost the cupcakes with a some additional frosting left over to play around with when you decorate your cupcakes. Any leftover frosting can be stored in the fridge for later and can even be frozen! This frosting works great for cupcakes, cookie cakes, frosted brownie bites, and more.Nutrition Facts below are estimated for the cupcakes only using an online recipe nutrition calculator. If all the frosting is used, it's about 261 additional calories per cupcake. Adjust as needed based on how much frosting you'd like to use and enjoy!