Prepare the aquafaba by measuring the liquid from two cans of chickpeas, simmer until reduced, and refrigerate overnight.

Preheat your oven to 150°C and line two baking sheets with parchment paper.

Whip the aquafaba with cream of tartar until frothy, gradually adding caster sugar until stiff peaks form.

Sift together ground almonds and icing sugar. Fold into whipped aquafaba without overmixing.

Pipe 2-inch circles of macaron batter on the baking sheets, resting at room temperature until a matte skin forms.

Bake in the preheated oven for 18 minutes, cool on the sheets before removing.

Beat together icing sugar, vegan margarine, and vanilla extract until fluffy, adding milk as needed.

Assemble by pairing macaron shells, piping buttercream between them, and pressing together.

Store in an airtight container for up to 2 days, letting sit at room temperature before serving.