In a large mixing bowl, sift together 2 cups of cake flour, 2 tsp of baking powder, 1/2 tsp of fine sea salt, and 1/2 tsp of ground nutmeg. Set aside once mixed.

In a stand mixer, cream together 1/2 cup of softened butter and 3/4 cup of granulated sugar on medium speed until sandy and light, about 2–3 minutes. Add in 2 egg yolks one at a time, mixing until fluffy.

Gradually add the sifted dry ingredients to the butter-sugar mixture, alternating with 1 cup of sour cream, mixing just until combined after each addition.

Wrap the dough tightly in plastic wrap and refrigerate for at least 1 hour.

On a lightly floured surface, roll out the chilled dough to about 1/2 inch thick. Use a doughnut cutter to cut out the doughnuts, placing them on parchment paper.

In a deep pot, heat 2–3 inches of canola oil to 325°F. Fry the doughnuts for about 2 minutes on each side until golden brown.

While frying, whisk together 1 cup of powdered sugar, 2 tbsp of corn syrup, 1/2 tsp of vanilla extract, and 2–3 tbsp of hot water until smooth. Dip each warm doughnut into the glaze.

Allow the glazed doughnuts to cool slightly on a wire rack. Serve them warm for the best flavor and texture.