Line a cookie sheet with a silicone mat (my favorite baking sheet for macarons and favorite silicone mats for macarons). I highly recommend a silicone mat of some kind, but if you don’t have one then you can also use parchment paper. In a food processor add the powdered sugar and almond flour and pulse until fully combined and rid of lumps. Sift the dry ingredients into a large bowl. If you don’t have a food processor you can just sift the ingredients together.
Whisk the poppy seeds into the dry ingredients.
In a medium bowl, prepare the french meringue. You can use a stand mixer for this, but I prefer a hand mixer for a batch this small. Beat the egg whites on low speed until they get frothy. Increase the speed and slowly add the sugar. If you add the sugar too fast you will deflate the meringue. Beat until stiff peaks form. This is when you pull the beater out and the meringue stands up with a slight curve. It should not fall or jiggle too much if you move the beater. If you want to add food coloring, do it now, but add it sparingly or you will make the meringue too liquidy.
Add the french meringue into the dry ingredients and begin to gently fold with a silicone spatula. This process is called macaronage. You will know the batter is ready when the ingredients are fully combined and not streaky. You should be able to hold the spatula above the bowl and draw a figure 8 smoothly without the batter breaking off. A good way to test if the batter is ready is to place a very small amount in your piping bag and pipe it onto your mat. If the batter is stiff and does not spread at all, then it is not ready. If the batter immediately runs out, then you have over folded. The batter should spread slightly and the tops should even out (there shouldn’t be any little tips sticking out), but it should not spread out too much.
Transfer the batter to a piping bag fitted with a piping tip (this is my favorite for macarons). Pipe 1-inch disks onto the prepared cookie sheet.
Firmly tap the cookie sheet onto the counter 3 or 4 times to bring any air bubbles to the surface. Use a toothpick to pop any remaining air bubbles.
Let the macarons rest for an hour. There needs to be a dry layer on the top. You should be able to run your finger over the top without any transferring to your finger. If it is really humid outside this process will likely take longer.
Preheat the oven to 280 degrees (F). This is the temperature that I have found works well for my oven, but you may need to play around with the temperature.
Place the macarons on the middle rack of the oven and bake for 5 minutes, rotate the cookie sheet, bake for another 5 minutes and rotate the cookie sheet again, bake for 5 minutes. 15 minutes in total. The macarons should not have any color to them, and they should peel off of the mat easily.
Remove from the oven and allow to cool completely.
Peel each macaron shell off of the mat and match each shell to another that is the same size.