For the ganache: Combine the chopped chocolate and butter in a heatproof bowl set over a pot with 1-inch of simmering water, making sure the bottom of the bowl does not touch the water. Cook, stirring occasionally, until melted and smooth. Stir in the cream, vanilla and salt, and then remove from the heat. Set aside until cooled and thickened, stirring occasionally, 30 to 45 minutes.

For the cookies: Position an oven rack in the center of the oven and preheat to 325 degrees F. Line 2 baking sheets with parchment paper. Using a small glass or cookie cutter (1 1/4 to 1 1/2-inch wide), trace 15 circles on each piece of parchment paper, leaving about 2 inches between each round. Flip the parchment over; the lines will be visible through the paper but you will not have to pipe directly onto the ink. Fit a pastry bag with a round tip about 1/4-inch wide.

Sift the confectioners' sugar and ground almonds into a bowl and discard any larger nut chunks. (If you have more than a tablespoon of bigger chunks, grind those until powdery and then resift.) Combine the egg whites and salt in the bowl of a stand mixer fitted with a whisk attachment (or in a large bowl with the whisk attachment of a hand-held electric mixer). Whip on medium-low speed until frothy, and then add the granulated sugar. Increase the speed to medium-high and whip until very soft peaks form. Add the almond extract and a few drops of food coloring if using. Whip until stiff peaks form. Fold about one-third of the sugar-nut mixture into the egg whites until blended, and then fold in the remaining two-thirds. The batter should be a bit fluid but not runny. It should slowly drip off the spatula and sit on top of the batter in the bowl for a bit before eventually oozing back into it. If it seems a bit stiff at this point, fold once or twice more until it relaxes, although be careful not to over fold. This correct texture is the key to the macaron and it is better to have a stiffer batter than a looser one.

Transfer the batter to the prepared pastry bag. Holding the bag perpendicular over the baking sheet, squeeze until the batter fills a circle drawn on the paper. Release the pressure on the bag and pull towards you to prevent a pointy tip on the center of the cookie. Repeat with the remaining circles. Gently flatten any points on the cookies with a damp fingertip.

Firmly rap the baking sheets against the counter to release any air bubbles and let stand at room temperature until the tops of the cookies no longer feel wet, 10 to 15 minutes. Bake, 1 sheet at a time, until the macarons are slightly crisp and the bottoms release from the parchment paper, about 15 minutes, rotating the sheet halfway through the baking time. Cool on the sheet 5 minutes, and then peel off the cookies and cool completely on a wire rack.

To assemble the cookies, spread a thin layer of the chocolate ganache on the bottoms of half of the cookies, about 1/4 teaspoon per cookie. Top with a second cookie, gently pressing to squeeze the ganache to the rims.

TIP: The weight of the batter in the pastry bag will force some of the batter out. To stop this, you can stick a mini marshmallow at the end of your pastry tip to block to the batter from running out the end.

TIP: You can use store-bought almond meal in place of the whole almonds. Sift 2/3 cup with the confectioners' sugar and, if necessary, grind the larger chunks and sift until a tablespoon or less of larger chunks remain in the sifter.

TIP: You can also spoon the batter onto the parchment lined baking sheets. The cookies may not be as perfectly round but will still taste great.