Tear off two large pieces of plastic wrap and set aside.
To make the dough, cream the ricotta and butter until smooth. Stir in vanilla, egg yolk, and sugar. Add flour, baking powder, salt, and cinnamon, and blend to create a soft dough that you can form into a ball. If too sticky to handle, add a little more flour. Divide the dough in half, roll each in a ball, and place each on the separate sheets of plastic wrap. Flatten with your hand to large disks. Wrap tightly and refrigerate for 2 hours or ideally overnight.
When ready to bake, preheat oven to 350 degrees. Line one large baking sheet or two smaller ones with parchment paper.
In a small bowl, combine the mascarpone, vanilla, and cinnamon until smooth.
To make the pastries, unwrap one dough disk and roll on a lightly floured surface or between two sheets of wax paper to a smidge less than 1/4-inch thick. Use a 3-inch drinking glass or biscuit cutter to cut rounds. Place 1 heaping teaspoon mascarpone mixture in the middle. Use your little finger or a small brush to apply a thin film of the beaten egg white along the outside 1/4–inch of the circle.
Fold in 3 edges to the center to form a triangle, leaving the top open. Firmly pinch the 3 points completely closed. Gently press the top of the triangle slightly down toward the filling (but keep the top open). Transfer to the prepared baking sheet. Repeat with remaining dough. (If the dough gets too soft, roll it between two sheets of wax paper and transfer the dough and paper to the freezer for 2-4 minutes before continuing.) Place the pan of shaped hamantashen in the freezer for 30 minutes. Remove and brush the tops and sides of the pastries with the beaten egg white.
Bake for 18 to 20 minutes, until tops and edges are lightly browned. Remove from oven and let the pastries rest on the pan for 8 to 10 minutes before transferring to a wire rack.
When completely cool, make the glaze. Place chocolate chips in a small cup or bowl and pour the piping hot espresso or coffee over top. Stir vigorously to melt the chocolate. Immediately pour 2 tablespoons of the espresso mixture over the confectioners’ sugar, stirring vigorously and adding more espresso a drop at a time as needed until the mixture becomes smooth and just liquid enough to drizzle. You will not need all the espresso mixture (it’s great to drink, though!). Drizzle the glaze in a loose pattern over the pastries and let stand until set.
These are best enjoyed the day they are made. To store, cover loosely (do not put in an airtight container, or they will get soft).
Unbaked hamantashen can be tightly wrapped and frozen and then baked later. To bake, remove from freezer, brush with beaten egg white, and bake, allowing an extra minute or two.