Rainbow Macarons

• Prep1 h
• Cook36 min
• Total3 h
• Serves28

Ingredients

For the shells

• 110 g superfine blanched almond flour (1 cup)
• 110 g powdered sugar (scant 1 cup)
• 100 g egg whites, at room temperature (from about 3 large eggs)
• 100 g granulated sugar (1/2 cup)
• 1/8 tsp cream of tartar, optional
• Gel food coloring in 5 colors, such as pink, orange, yellow, green and purple

Vanilla buttercream

• 115 g unsalted butter, softened (1/2 cup, 1 stick)
• 160 g powdered sugar (1 1/3 cups)
• 15 g heavy cream or whole milk (1 tbsp)
• 1 tsp vanilla extract
• 1 pinch salt

Instructions

1. Line 2 baking sheets with parchment paper or silicone mats. Place the almond flour and powdered sugar in the clean, dry mixing bowl and blend 10 sec/speed 10. Sift into a large bowl, pressing the mixture through with a spoon, and discard any coarse bits left in the sieve (1 tbsp at most).
2. Wash and dry the mixing bowl and butterfly whisk, then wipe both with a paper towel dampened with lemon juice or vinegar, since any trace of fat keeps the whites from whipping. Insert the butterfly whisk, add the egg whites, granulated sugar and cream of tartar and whip 5 min/50°C (122°F)/speed 3.5.
3. Remove the measuring cup and whip 8 min/speed 4, until the meringue is thick and glossy, holds stiff peaks and the bowl feels only barely warm.
4. Remove the butterfly whisk and scrape the meringue onto the almond mixture. Fold with a large spatula, pressing the batter against the side of the bowl, about 30 strokes, until no dry almond flour shows but the batter is still thick. Divide it among 5 small bowls, add a small dot of a different gel color to each and fold 5 to 10 strokes more, until the batter flows off the spatula in a thick ribbon that sinks back into itself in about 10 seconds.
5. Spoon each color into its own piping bag with a 1 cm (1/2 in) round tip, or a bag with the corner snipped, and pipe 3.5 cm (1 1/2 in) rounds about 3 cm (1 1/4 in) apart. Rap each sheet firmly on the counter 4 times and pop any bubbles with a toothpick. Let them rest 30 to 60 minutes, until the tops no longer feel sticky, and meanwhile preheat the oven to 150°C (300°F).
6. Bake one sheet at a time on the middle rack for 16 to 18 minutes, until the shells have risen on their ruffled feet and peel off the paper cleanly. Let them cool completely on the sheet.
7. Wash and dry the mixing bowl. Insert the butterfly whisk, add the butter and whip 1 min/speed 3.5. Add the powdered sugar, cream, vanilla and salt, put the measuring cup in place and whip 2 min/speed 3.5, scraping down halfway, until light and fluffy.
8. Pair the shells by color and size. Pipe a 1.5 cm (1/2 in) mound of buttercream on half of them and gently press the matching shells on top. Refrigerate in an airtight container for 24 hours, so the filling softens the shells into the classic chewy texture.
9. Take the macarons out of the refrigerator 20 minutes before serving and arrange them on a white tray in rows, one row per color.

Tips

• Central Florida humidity slows the drying time. Run the air conditioning or a fan nearby; on rainy days the shells may need up to 90 minutes before they feel dry to the touch.
• Use gel or powder colors, never liquid food coloring, and separate fresh eggs for the whites: liquid color and whites from a carton make the batter runny.
• Every oven runs differently. If the tops brown, lower the temperature by 10°C (about 20°F) and bake a little longer; if the shells stick to the paper, give them 2 more minutes.
• Filled macarons keep 5 days in the refrigerator or 1 month in the freezer in an airtight container. Thaw them in the refrigerator without opening the container, so they stay dry.