Using a mixer with a dough hook, knead flour, yeast, sugar, sour cream, milk, egg, butter, brandy, and salt at low-medium speed for 10–12 minutes until smooth dough forms.

Cover bowl and let rise one to two hours until doubled in size.

Transfer dough to work surface and divide into 20–25 equal pieces.

Roll each piece of dough into a tight ball and place on a pan lined with well-greased baking paper.

Grease tops of balls and let rise one hour or until puffy.

Heat oil in a medium-sized pot to 350 degrees Fahrenheit (180 degrees Celsius). If you don’t have a thermometer, test the oil by inserting a wooden spoon. If small bubbles form around it, oil is hot enough.

Fry donuts in hot oil until golden on all sides.

Remove donuts from oil with slatted spoon. Drain on plate lined with absorbent paper. Let donuts cool to room temperature.

Put one cup (250 milliliters) heavy cream and chocolate squares into a medium-sized bowl. Melt in microwave or double boiler until completely melted and smooth.

Refrigerate ganache for one to two hours or until completely cool.

Transfer cold ganache to mixer bowl and add remaining half cup (125 milliliters) heavy cream. 

Beat on high speed until very stiff, smooth cream forms.

Transfer chocolate cream to pastry bag with a smooth, half-inch (one-centimeter) tip. Fill donuts with a generous amount of cream.

Break chocolate into squares and melt in microwave or double boiler. When completely melted, add oil and mix.

Transfer chocolate mixture to pastry bag (without a tip), and drizzle thin stripes on donuts.

Beat heavy cream and confectioners’ sugar in mixer until very stiff.

Transfer to pastry bag with half-an-inch to one-inch (one- to two-centimeter) serrated tip, and pipe small mounds on top of donuts.

Garnish with a little grated chocolate and serve. Donuts are best the day they’re made.