Preheat oven to 375 degrees then coat a 10" x 15" jelly roll or sheet pan with cooking spray. Add butter and water to a large saucepan then place over medium heat. Bring to a boil, then remove from heat and stir in flour, sugar and sour cream until smooth.
Add beaten eggs, vanilla, salt and baking soda and stir until smooth. Spread batter evenly into prepared baking dish and bake 20–22 minutes until golden brown and firm in center. Rinse and dry saucepan to use when making the glaze.
Remove cake from oven and cool on a rack for 10–15 minutes.
For the glaze, place butter in a medium saucepan and melt over medium heat. Continue heating until butter just barely begins to turn brown on the bottom then immediately remove from heat and add milk. Stir to combine. Add powdered sugar and vanilla paste and mix until a smooth and pourable glaze forms. If necessary, add a bit more milk to thin, or a bit more powdered sugar to thicken glaze to proper consistency. Pour glaze over slightly warm cake and spread into an even layer. Allow cake to cool completely before slicing and serving.
Notes
Texas sheet cake is typically chocolate, however we changed it to a vanilla cake and kept the name!