Preheat your oven to 350°F (175°C). Grease and flour a 10x15-inch cake pan.
Mix flour, brown sugar, peanut butter, and butter with an electric mixer on low until crumbly.
Add milk, vanilla, and eggs. Mix on low until combined, then beat on medium for 3 minutes until smooth.
Pour batter into the prepared pan and bake for 35-40 minutes, or until a toothpick comes out clean.
Warm peanut butter and honey in the microwave, then stir in vanilla, powdered sugar, and milk until smooth.
Let the cake cool for 10 minutes, then spread the frosting over the warm cake. Sprinkle mini chocolate chips over the frosting and let the cake cool completely before slicing.