If you have not fried pistachios, then bake them in the oven for 8-10 minutes at 180 degrees. so that their taste is saturated, and so it will be easier to remove the husk.
Melt the chocolate and butter in a water bath.
Remove from the heat. Add sugar and stir. You can take any sugar.
Add the eggs one by one, mixing thoroughly with a whisk after each.
Add flour and mix.
Prepare a baking dish. It can be any: rectangular, square or round. The size is about 22-24 cm in diameter. Cover it with baking paper.
Put half of the dough, then pistachios, then the second half of the dough.
Bake brownies for 30 minutes at a temperature of 150 degrees. Remove, cool slightly, remove the paper, cut into triangles.
Insert the tube into the brownie base.
Prepare the glaze: mix the egg white and powdered sugar, stir with a whisk until thickened. You may need some more powder.
For a more festive look, you need to add green paint. If you are against dyes, then just leave the white glaze.
Transfer the glaze into a pastry bag, make brownie patterns in the form of garlands. Decorate with pastry sprinkles.