Line two baking sheets with silicone macaron mats.
Wipe the inside of the mixer bowl and whisk attachment with white vinegar.
Fit a piping bag with a coupler, no piping tip.
In the bowl of a food processor, combine the powdered sugar, cocoa powder, almond flour and avocado OR canola oil. Process for 30 seconds or until well blended. Sift the ingredients onto a sheet of parchment paper, then pour them in a bowl and set aside.
Place the egg whites and the granulated sugar into the mixer bowl. Beat on medium-low speed for about 3 minutes. Turn the mixer up to medium and beat for about two minutes - until the meringue has some volume. Turn the mixer up to high and beat until the meringue holds a stiff peak, about 2-3 more minutes. (The meringue will stand straight up if you dip a spoon in and lift up). Add the food gel if you're using it, and beat until just combined.
Scrape down the sides of the bowl with a rubber spatula and fold in 1/4 of the almond mixture. Once barely mixed in, add another quarter of the mixture, fold in, and repeat until all the almond mixture has been folded in. Make sure to scrape the spatula down on the rim of the bowl once in a while to help prevent clumps from forming. Continue to fold until the batter has deflated and become softer, but be careful not to over mix. To test if the batter is ready, lift the spatula and let some of the batter drizzle down; it should flow gently like lava and almost disappear in about 30 seconds. Another test - if you lift your spatula and let the batter drip, the batter should be loose enough that you are able to just barely draw a figure 8 with it. If it's too thick, it won't drizzle enough to draw that 8.
Fill your piping bag with the batter. Hold the piping bag upright, with the tip hovering over the mat about 1/2 inch, and squeeze out the batter onto the center of the circle template, stopping a bit before you get to the edges of the lines.
Once all your batter has been piped, gently rap the baking sheet on the table 3-4 times. This helps pop some of the air bubbles.
Allow the macarons to sit at room temperature for about 3o minutes. They should develop a "skin" or not be wet to the touch, when you bake them.
While the macarons are resting, preheat your oven to 300 degrees Fahrenheit (150 degrees Celsius).
Place the macarons in the oven and bake for 9 minutes. Then rotate the baking sheets from front to back and top to bottom. Bake for another 15 minutes.
Allow the macarons to completely cool before removing from the mat.
Remove the macarons by gently and slowly lifting them off the mat. It can help to lift the mat and peel it away from the macaron.
Keep the macaron shells in an airtight container for 2 days or in the freezer for up to 3 months or fill and serve them right away.