Place the chickpea liquid in a saucepan and heat over medium heat to reduce by half.

Let it cool and then refrigerate for at least 1 hour.

Sift the almond flour and powdered sugar into a bowl to remove any lumps. Optionally, blend in a food processor to ensure a fine powder.

Once the aquafaba is chilled, place it in the bowl of a stand mixer and whisk at medium speed until soft peaks form. You can also use a handheld mixer.

Gradually add the granulated sugar and continue whisking at high speed until you achieve stiff peaks.

Add the spirulina or food coloring and whisk again to incorporate.

Gently fold the almond flour and powdered sugar mixture into the whipped aquafaba in two batches using a spatula. Mix until the batter is smooth and shiny, forming a ribbon when it falls from the spatula.

Transfer the batter to a piping bag fitted with a round tip.

Pipe small rounds of batter, about the size of a coin, onto a baking sheet lined with parchment paper. Tap the baking sheet gently on the counter to smooth the tops and release any air bubbles.

Let the macaron shells dry at room temperature for about 30 minutes to 1 hour, until they are dry to the touch.

Preheat the oven to 120°C (250°F).

Bake the macaron shells for 15 to 18 minutes, rotating the baking sheet halfway through to ensure even baking.

Once the "feet" (ruffled base) have formed, turn off the oven and leave the macarons inside with the door closed for 15 minutes.

Allow the shells to cool completely before gently peeling them off the parchment paper.

In a large bowl, beat the vegan margarine with an electric mixer until creamy.

Gradually add the powdered sugar, beating well after each addition.

Incorporate the cocoa powder. Beat until light and fluffy.

Transfer the buttercream to a piping bag fitted with a round tip.

Pipe a small amount of buttercream onto half of the macaron shells, then sandwich them with the remaining shells, pressing gently to spread the filling.