Vanilla Winter Spice Bars — Buzzed Eats

Name: Vanilla Winter Spice Bars — Buzzed Eats
Cuisine: Thai, Asian
Ingredients: 1 1/2 Cup Flour; 1 1/2 Tsp Cornstarch; 1/2 Tsp Baking powder; 1/8 Tsp Baking soda; 3/4 Cup Sugar; 1/4 Tsp salt; 2 Tsp Buzzed Eats Brew Enhancer Spice Mix (or similar spice blend); 1/2 Cup butter (very soft); 1 Egg (room temperature); 1 1/2 Tsp Vanilla extract; 6 Tbsp Butter (very soft); 1/8 Tsp salt; 1/4 Tsp Buzzed Eats Brew Enhancer Spice Mix (or similar spice blend); 1 1/2 Cups Powdered Sugar; 1 Tbsp Whole Milk; Stand mixer with a paddle attachment; Mixing bowls; Rubber scraper; Measuring cups; Measuring spoons; Spray grease or neutral oil (vegetable, canola, etc); 8X8 Baking pan; Parchment paper (cut in a long strip the width of the pan base); Whisk