Sweetened Condensed Milk

This is a recipe I found somewhere in an old cookbook when I still lived at home (before I got married).
The main reason I have kept this recipe is A-the ingredients are something I always have on hand and B-this makes it convenient. I  never run out when a recipe calls for it!
1 Cup powdered milk
1/3 cup boiling water
2/3 cup white sugar
2 1/2 tablespoons butter (unsalted and real butter)
Add the above ingredients into a blender and blend until the sugar dissolves. This recipe makes what would be one can of sweetened condensed milk. If you try this let me know if you like it! :)