Combine 1 1/2 cups softened butter and cream cheese in a large bowl.

Beat with an electric mixer until creamy.

Beat in flour until dough comes together.

Wrap dough with plastic wrap and refrigerate until firm, about 1 hour.

Preheat oven to 325 degrees F (165 degrees C).

Spray three 24-cup mini muffin tins with cooking spray.

Combine brown sugar, eggs, 1/4 cup melted butter, vanilla extract, and salt in a large bowl to make filling.

Beat with an electric mixer until smooth.

Shape chilled dough into 1-inch balls.

Press 1 ball of dough over the bottom and up the sides of each muffin cup.

Spoon 1 teaspoon walnuts over the dough.

Drop 1 teaspoonful of the filling on top.

Bake in the preheated oven until the crust begins to turn golden and the filling is bubbling slightly, 25 to 30 minutes.

Cool for 10 minutes before serving.