Prepare the Dough:

In a mixing bowl, beat the butter and cream cheese until smooth.

Add the egg yolk and mix until combined.

Slowly add the flour and mix until a soft dough forms.

Cover and chill the dough for about 30 minutes.

Make the Filling:

In a separate bowl, whisk the melted butter and eggs together.

Stir in the brown sugar and vanilla extract until smooth.

Fold in the chopped pecans until evenly mixed.

Assemble the Tassies:

Preheat your oven to 350°F (175°C).

Grease mini muffin tins or line them with paper liners.

Roll the dough into 1-inch balls and press them into the muffin cups to form small shells.

Fill each shell with the pecan mixture, leaving a bit of space at the top.

Bake:

Bake for 20-25 minutes or until the filling is set and the edges of the crust are golden.

Let the tassies cool in the pan for a few minutes before transferring them to a wire rack to cool completely.