Coffee macarons (Pierre Hermé)

This summer, I spent a few days at my in-laws, which gave me the opportunity to make my first Italian meringue macarons à la Pierre Hermé. Indeed, I think I mentioned in some of my recipes that I only have a (very) old gas oven at home, so with approximate temperatures and, of course, no convection heat. Needless to say, macarons were mission impossible! So, I took advantage of a recently updated oven to make macarons, and here's the recipe I used:

For about twenty macarons:

Macaron Shells:

55g egg whites (1)
55g egg whites (2)
150g granulated sugar
35g water
150g almond powder
150g icing sugar
Food coloring (optional)

It is often recommended to separate egg whites from yolks several days in advance and keep the whites in an airtight container in the refrigerator. Since I wasn't at home to make these macarons, I did this step only the day before making the macarons, but feel free to do it a bit in advance if you can!
Start by sifting the almond powder and icing sugar.

Separately, prepare the sugar syrup: heat the water and granulated sugar. When the temperature reaches 110°C, start whisking the 55g of egg whites (1) until they are foamy but not completely firm. When the syrup reaches 121°C, pour it over the egg whites while continuing to beat. Keep beating your Italian meringue until cooled (it should be smooth, shiny, and form a nice bird's beak).

Mix the 55g of egg whites (2) with the almond powder and icing sugar.

Then, gently incorporate your desired food coloring (you can make the color quite intense as it tends to lose some vibrancy during baking) and the Italian meringue into your mixture.

The resulting batter should be smooth and shiny. At this point, I encountered a small difficulty, perhaps due to the heat when making these macarons: I hadn't yet added all the Italian meringue, but my batter was already quite smooth and formed a ribbon. So I decided not to add the rest of the meringue for fear of having too runny a batter. It was my first macaron attempt, and I will have to try this recipe again in cooler temperatures to see if that was the issue.
You can then place your macaron mixture in a piping bag fitted with a plain tip and pipe your macarons onto a parchment-covered baking sheet.
Regarding baking, I had read many different things; personally, I baked my macarons at 140°C on convection heat for 10 to 12 minutes. If this baking time does not suit you, you will have to do trials to find the ideal temperature for your oven to bake macaron shells.

Coffee Ganache:

120g of good quality white chocolate (the ideal being Valrhona's Ivoire)
100g of heavy cream
6g of coffee powder

Melt the chocolate in a double boiler or microwave.
Bring the cream to a boil with the coffee powder.

Once the cream is hot, strain it to remove some of the coffee grounds, then pour it over the white chocolate, stirring well to homogenize the mixture. Then refrigerate until use.
My coffee ganache did not solidify completely, so filling the macarons was a bit challenging, especially with the ambient temperature. Next time, I might add a bit more chocolate (even if it means compensating with an additional 2g of coffee in the cream) to have a slightly firmer, more manageable ganache.