In a medium bowl, add in the butter and cream cheese. Beat with a hand mixer until creamed.
Add in the flour and beat until a dough forms. This will take 1 to 2 minutes and will look crumbly before it comes together.
Using a 1 tablespoon cookie scoop, scoop the dough and place into each cavity of a mini muffin pan.
Using the smaller side of a tamper or a medicine cup if you don't have a tamper, press the dough into the bottom and up the sides of the mini muffin cavity. Set aside.
Filling
Add the egg, brown sugar, and melted butter into a medium bowl. Whisk to combine.
Add in the pecans and stir until incorporated.
Add a heaping teaspoon of filling to each crust.
Place into the preheated oven and bake for 25 to 30 minutes until the crust is golden and the filling is puffed. Let cool in the pan for 10 minutes.
If the crust was overfilled and the pecan filling stuck to the side of the pan, gently slide a knife between the pan and the tassie to release the tassie.
Remove from the pan and let cool completely on a paper towel or wire rack.