Hot Chocolate Cookies

Adjust the oven rack to the middle position and preheat the oven to 350°F (180°C). Line two large baking sheets with parchment paper.

Make the chocolate filling: In a saucepan over low heat, gently melt the chopped dark chocolate, heavy cream and butter together until the chocolate is fully melted. If the mixture looks slightly split, that's okay.

Pour the melted chocolate mixture into a bowl and let it cool until warm (not hot). Add the sugar, egg, vanilla and salt, and whisk gently (avoid aerating) until smooth and glossy. Set aside at room temperature until needed.

Make the cookie dough: In a large bowl, cream the softened butter and light brown sugar until pale and fluffy (by hand, with a hand mixer, or stand mixer with paddle attachment).

Add the egg yolks and vanilla to the creamed butter and sugar and mix until combined.

In a separate bowl, whisk together the all-purpose flour, Dutch-processed cocoa powder, baking powder and salt. Add the dry ingredients to the wet ingredients and mix until you have a smooth, scoopable cookie dough with no flour clumps. The dough should be firm enough to shape but not dry or crumbly.

Pour the granulated sugar for rolling into a small bowl. Using a 2-tablespoon cookie scoop (or a 2 tbsp measure), portion the dough, roll between your palms to form a ball, then roll the ball in the granulated sugar to coat.

Place each sugar-coated dough ball on the prepared baking sheet and use a 1-tablespoon measuring spoon to make an indent in the center of each ball. Repeat to make 18 cookies total, spacing them about 2 inches (5 cm) apart.

If the chocolate filling has firmed up too much while assembling, loosen it by placing the bowl into a larger bowl or plate of hot water (ensure no water gets into the filling) and stir until it reaches a loose but not fully runny consistency. Do not microwave the filling (that can scramble the egg).

Fill each cookie indent with about 1 tablespoon of the chocolate filling (it will be full to the brim). There should be no filling left over.

Bake one sheet at a time at 350°F (180°C) for 8–9 minutes, or until the cookies have spread and puffed slightly and the chocolate filling is still slightly wobbly when you gently shake the baking sheet.

Remove from the oven and allow the cookies to cool on the baking sheet until warm — they will be very soft and fragile immediately out of the oven. Moving them too soon can cause them to break.

Make the Swiss meringue (recommended to do just before serving): Place the egg whites, sugar and cream of tartar in a heatproof bowl set over a pot of simmering water (double-boiler). Whisk constantly until the mixture reaches 160°F (70°C) and the sugar has dissolved.

Transfer the hot egg-white mixture to a stand mixer fitted with the whisk attachment (or use a hand mixer) and whisk on high for 5–7 minutes until greatly increased in volume and stiff peaks form. Add the vanilla and whisk briefly to combine.

Transfer the Swiss meringue to a piping bag fitted with your chosen tip. Pipe dollops or decorative shapes onto the warm or room-temperature cookies, then toast the meringue with a kitchen torch until golden.

Serve the cookies warm, at room temperature, or chilled. Reheat for 5–10 seconds in the microwave for an extra-gooey centre, if desired.