Preheat the oven to 400°F and line a baking sheet with parchment paper.
In a large bowl, whisk together the flour, baking powder, salt, and cinnamon.
Add the cubed butter to the bowl, and use a pastry cutter to cut the butter into the flour. You will want to work it until the mixture is crumbly, like a coarse meal with some pea sized chunks in there as well.
In a separate, smaller bowl, whisk together the yogurt, milk, and vanilla.
Add the yogurt & milk mixture to the flour mixture and begin stirring it with a fork until a dough just starts to come together. There will be large clumps and that's okay! Add the chopped plums and fold them into the dough clumps. There's no need to work the plums in too much, just a few gentle fold into the dough will do. Try to avoid overworking the dough.
Dump the dough onto a lightly floured surface. Use your hands to press it together, until it forms a 1" tall rectangle. Do not knead the dough.
Use a sharp knife to cut it into 8 triangles, or 8 squares. In this case, I went with squares, but do whatever you feel!
Optional (but recommended): freeze the scones for 10-15 minutes before baking.
Transfer the scones to the baking sheet, leaving 1"-2" of space between each. Brush the tops with some milk and sprinkle with turbinado sugar and cinnamon. Bake for 15 minutes, or until they start to turn golden brown.
Let the scones cool down until they're slightly warm before topping with icing.
To making the icing glaze, whisk the honey, powdered sugar, milk, and vanilla together in a small bowl. Top each scone with a spoonful of the honey glaze.
Enjoy!