For the crust: 

You might not use all of it. You can make cookies with the leftovers. 

1. In a large bowl beat butter with sugar for a minute.
2. Add egg and vanilla and mix well.
3. Sift the dry ingredients or flour mixture: flour, cinnamon, and salt and add them in two parts to the butter mixture. Then add the nuts.
4. Mix everything together but don’t overwork the dough. It may be soft.
5. Pat it into a flat round, wrap in plastic, and refrigerate for at least an hour, until it relaxes and hardens.

For the filling:

1. Have ready a 9-inch square dish (I use glass or ceramic). 
2. Add the sliced plums and distribute them evenly. 
3. Sprinkle with the sugar, cornstarch, juice, zest, and cinnamon if using. Lightly stir everything to combine. 

Assembling the cobbler:

1. Preheat the oven to 350°F/180ºC.
2. On a lightly floured counter, roll out the cold dough (if it’s too hard when taking it out from the refrigerator, let it soften slightly, just until you can begin to roll it) sprinkling with additional flour if it sticks to the counter. 
3. Roll it about 1/4 inch thick.
4. Cut any shape you want and immediately top the cobbler with the dough pieces. Make sure you leave spaces without topping as the fruit juices need to evaporate during baking and bubble up. 
5. Bake for about 40-45 minutes, until the fruit is bubbling and the cookie topping is golden and dry. 
6. Eat warm with a scoop of ice cream or plain at room temperature. 
7. Refrigerate leftovers, covered in plastic warp or in an airtight container.