Warm the milk until it is lukewarm, not hot. Add the dry yeast and 1 teaspoon of the 90 g sugar, then stir until the yeast has dissolved. Leave the mixture to sit for a few minutes, until the yeast looks slightly foamy on top.

Add the instant coffee to the warm yeast milk and stir until fully dissolved. Add the medium egg, vanilla extract, and remaining sugar. Then add the flour and water and mix everything together until a rough dough forms.

Knead the dough by hand or with a stand mixer fitted with a dough hook. Once the dough has come together and is well combined, add the softened butter gradually while continuing to knead. Keep kneading until the butter is fully incorporated and the dough is smooth, soft, elastic, and slightly tacky. If it sticks to your hands, lightly oil your hands instead of adding more flour.

Shape the dough into a ball and place it in a lightly greased bowl. Cover the bowl and let the dough rise in a warm place until doubled in size and visibly puffy. The rising time depends on the temperature of your kitchen.

Dissolve the instant coffee for the filling in a very small splash of water and let it cool. Add the softened butter, brown sugar, cinnamon, cocoa powder, cooled coffee mixture, and vanilla extract to a bowl. Mix until smooth, creamy, and spreadable.

Transfer the risen dough to a lightly floured work surface. Roll it into a large rectangle. Try to keep the thickness even so the rolls bake evenly and have neat spirals.

Spread the filling evenly over the dough, leaving a small border along one long edge. Roll the dough tightly from the opposite long edge into a log. Cut the log into even rolls using a sharp knife or unflavored dental floss. Arrange the rolls in a greased baking dish, leaving a little space between each one.

Cover the baking dish and let the rolls rise again until puffy. Toward the end of the rising time, preheat the oven to 175°C. Just before baking, pour 30 to 50 g heavy cream evenly over the risen rolls. The cream soaks into the dough during baking and creates an especially soft, rich, gooey center.

Bake the rolls at 175°C for 26 minutes, until lightly golden and baked through. Remove the baking dish from the oven and loosely cover the rolls. Leave them to cool in the dish for about 1 hour, until they are no longer warm.

Once the rolls have cooled, add the mascarpone, heavy cream, powdered sugar, and vanilla extract to a mixing bowl. Whip everything together until thick, creamy, fluffy, and spreadable. Do not overmix. Stop once the frosting holds its shape.

Spread the mascarpone frosting generously over the cooled cinnamon rolls. Finish with a light dusting of cocoa powder just before serving. Serve immediately and enjoy.