Heat 1 tbsp butter in a large saute pan over medium heat. Saute onions for about 3 minutes , until golden.
Add another 1 tbsp butter and the olive oil to the pan. Add the mushrooms and saute for about 3-5 minutes, stirring frequently until browned. Remove from pan and set aside in a bowl.
Keeping the pan over medium heat, add 2 tbsp butter and stir until melted. Add flour and continue stirring until bubbly and foaming. Add beef broth and whisk until smooth and starting to thicken. Add mushroom mixture back to pan and thyme leaves. Salt and pepper to taste. Set aside to cool.
Roll Dough and Fill
Remove your dough from the fridge and cut into 2 equal parts. Then, cut each into another 5 equal pieces.
Roll each piece into a 4 inch round, use small plate or bowl and cut around the edges.
Fill each round with 1/4 cup mixture and 1 tbsp white cheddar cheese. Fold in half and press edges down to seal. Using a fork press against the edge to crimp and seal. Slice 2-3 thin air holes in the top. Place in freezer for 15 minutes before baking.
Bake at 400 degrees for about 10 minutes or until golden brown. Freeze any extras for later use.