Preheat oven to 350F (175C) and very thoroughly grease and flour a 12-cup bundt pan (be sure to tap/shake out excess flour).

In the bowl of a stand mixer or in a large bowl using an electric mixer, combine butter, cream cheese, and sugar and beat on medium-speed until well-combined and batter is lightened in color.

Add eggs, one at a time, stirring well after each addition (about 10 seconds on medium-speed after each addition). Scrape the sides and bottom of the bowl and stir in vanilla extract. Mixture should be very smooth, light, and creamy when finished.

In a separate bowl, whisk together flour, baking powder, and salt.

With mixer on low-speed, alternate adding the flour mixture and milk mixture to the butter batter, starting and ending with the flour mixture (I usually add the flour in 3 parts and the milk in 2). Pour batter into prepared bundt pan and bake on 350F (175C) for 50-60 minutes or until a wooden skewer inserted in the thickest part of the cake comes out clean or (preferably) with a few moist crumbs. If you have a lighter-colored bundt pan, it may take longer in the oven.

Allow to cool for 15-30 minutes then carefully invert onto cooling rack to cool completely before covering with glaze.

Prepare glaze by whisking together powdered sugar, melted butter, and vanilla extract. Add milk, one tablespoon at a time, until consistency is thin enough that it falls in ribbons off of whisk but holds its shape for several seconds before melting back into the bowl.

Drizzle over cooled bundt cake, allow glaze to set for 30-60 minutes (this may be faster or longer, depending on the precise thickness of your glaze) and then dig in!