- Preheat the oven to 425, as directed on the package of puff pastry 
- Lay out the puff pastry, and cut 6 equal rectangles. Lightly grease a muffin tin. Set both aside. 
- Cook the italian sausage until done. Set aside. 
- In the same pan, cook the leek slices with 1 tbsp butter until transluscent. 
- While the sausage and leeks are cooking, cut the potatoes into 1/4 inch cubes. 
- Line 6 muffin cups with the puff pastry. Press it gently down into the cup. 
- Layer in each cup: sausage, leeks, and potatoes. You should be able to do 2 thin layers in each cup. They will be heaping full. 
- Divide the remaining butter into thirds and put a piece on top of each muffin cup. 
- Fold the puff pastry over the top. You can gently pull and press the pastry so that it will completely cover the sides. Do leave a hole in the top for steam to escape! 
- Brush each mini galette with milk. Bake at 425 for 15-20 minutes, until the pastry is golden brown.