Cook butter over medium heat, swirling occasionally until it turns deep amber with a nutty aroma (5-7 minutes), then immediately pour into a bowl to stop cooking—this prevents burning and ensures consistent flavor across all three components.

Bring eggs, sour cream, and milk to room temperature before mixing to ensure proper emulsification and a tender, evenly-textured crumb that won't be dense or gummy.

Use chilled brown butter and work it into the flour mixture with your fingertips until it resembles coarse sand, then chill the streusel for 15 minutes before baking to prevent it from melting into the batter and maintain that desirable crumbly topping.

Add powdered sugar to cooled brown butter one cup at a time while whisking, then adjust with heavy cream by the teaspoon until it reaches a pourable consistency that pools slightly but doesn't run completely off the cake.

Let the cake cool for 10-15 minutes before glazing—warm cake will cause the glaze to melt immediately, while completely cool cake prevents proper glaze adherence and creates a thick shell instead of that elegant melting effect.