Preheat your oven to 375°F (190°C). Have a 24-cup mini muffin tin ready.
Unroll the phyllo dough on a clean work surface. To prevent it from drying out, cover the stack with a clean, slightly damp kitchen towel while you work.
Place one sheet of phyllo on your work surface. Lightly brush it all over with melted butter and sprinkle with about 2 teaspoons of sugar. Place another sheet directly on top, brush with butter, and sprinkle with sugar. Repeat one more time for a total of 3 layers.
Using a sharp knife or pizza cutter, cut the layered phyllo stack into 12 equal squares (approximately 3x3 inches).
Gently press each square into a cup of the mini muffin tin, ruffling the edges to fit. The corners will stick up.
Repeat the layering and cutting process with the remaining 3 sheets of phyllo and remaining butter and sugar to fill all 24 mini muffin cups.
Bake for 15-20 minutes, or until the cups are golden brown and crisp. Let them cool completely in the pan before carefully removing them.
While the cups cool, make the filling. In a medium bowl, whisk the instant espresso powder with 1 tablespoon of the heavy cream until it has dissolved.
Add the remaining heavy cream, cold mascarpone, sweetened condensed milk, cinnamon, and optional coffee liqueur to the bowl. Using an electric mixer, beat on medium-high speed until stiff peaks form, about 2-3 minutes.
Just before serving, pipe or spoon the coffee cream into the cooled phyllo cups. Dust with cocoa powder and serve immediately for the best texture.