Preheat your oven to 350°F (175°C). Line your baking sheet with parchment paper.

In a large mixing bowl, cream together the softened butter, vegetable oil, and brown sugar until light and fluffy. Beat in the egg and vanilla extract until well combined. Gradually stir in cinnamon, baking soda, baking powder, salt, and flour until just incorporated.

In another bowl, mix together the cold butter, brown sugar, flour, cinnamon, and a pinch of salt for the streusel topping until crumbly.

Use a cookie scoop to portion out the cookie dough and place balls onto the lined baking sheet, pressing your thumb into the center of each cookie for indentations. Fill each indent with streusel mixture.

Bake for 10-12 minutes or until the edges are golden and centers are set.

While cooling, whisk together powdered sugar, milk, and vanilla extract for the icing until smooth.

Drizzle the icing generously over the cooled cookies for a delightful finish.