In a medium sauce pan on low to medium heat, combine the butter and the loose tea leaves until the butter melts. Reduce to low heat and allow to simmer for 5 minutes.
Remove from the heat and let the tea steep for another 5 minutes.
Strain the butter through a fine-mesh-sieve set over a bowl and refrigerate until it reaches softened butter consistency – 20 to 30 minutes.
Place the egg whites and sugar in the bowl of a stand mixer, whisking to combine.
Fill a medium saucepan with water and place it over medium-high heat.
Place the stand mixer bowl on top, creating a double-boiler effect (the bowl shouldn’t touch the water.)
Whisking intermittently, heat the egg mixture until it registers 160 degrees Fahrenheit (70 degrees Celsius) on a candy thermometer.
Carefully move the mixer bowl back to the stand mixer.
Using the whisk attachment, beat the egg white and sugar mixture on high speed for about 8-10 minutes until it reaches medium-stiff peaks. The mixture should have cooled down now to room temperature.
If making meringue kisses, fill a piping bag fitted with a star tip with up to one cup of meringue. Pipe drop stars on parchment paper lined baking sheet and bake until dried out and crisp.
On the stand mixer, swap out the whisk attachment for the paddle attachment.
With the mixer on low speed, add the vanilla paste, tea infused butter and remaining 1 cup of butter about a tablespoon at a time.
Once incorporated, add the coffee extract, pinch of salt, then the first tablespoon of coffee milk tea and turn the mixer to medium-high and beat to combine; add the final tablespoon and beat on medium high until buttercream is thick and lustrous.