# Steps to Follow:
01 - Preheat oven to 350°F. Line baking sheets with parchment paper.
02 - Beat softened butter, vegetable oil, and brown sugar in large mixing bowl until light and fluffy.
03 - Mix in egg and vanilla extract until fully incorporated.
04 - Whisk together flour, cinnamon, baking soda, baking powder, and salt in separate bowl.
05 - Gradually add dry ingredients to wet mixture, stirring until just combined.
06 - Combine softened butter, brown sugar, flour, cinnamon, and salt in bowl. Mix until crumbly texture forms.
07 - Drop dough onto prepared baking sheets using 1½ tablespoons per cookie. Press indent into center of each.
08 - Fill each center indentation generously with streusel mixture.
09 - Bake 10-12 minutes until edges are lightly golden.
10 - Let cool on baking sheet 5 minutes, then transfer to wire rack. Whisk powdered sugar, milk, and vanilla until smooth. Drizzle over cooled cookies.