Blondie Biscuits

This morning I discovered an empty biscuit tin when I went to pack lunches. Apparently we have a very large and dexterous mouse adept at opening lids, as everyone denied all knowledge of eating the last of them.
Feeling all Stepford Wife at 7.30am (though would a Stepford have let it get in that state in the first place? ) I found a quick recipe using ingredients I already had. It's a recipe for Blondies, but I made it in a larger tin, thereby making them more biscuit-like.

Ingredients:
half cup melted butter
1 cup packed dark brown sugar (I only had light brown, so I added a tablespoon of treacle)
1 cup self raising flour (or plain with 1tsp baking powder)
1 beaten egg
1 tsp vanilla extract

1. Preheat oven to 175C.
2. Grease and line tin. Mine is 9.5in x 12.5in. If you used an 8in x 8in tin they would be more like blondies.
3. stir sugar into melted butter until smooth
4. add egg and vanilla and mix well
5. add flour
6. add any extras. I had half a bag of choc chips so I put those in, but you can use nuts or just leave them plain
7. Pour into tin. Don't worry if it doesn't all reach the corners. It will spread when cooking.
8. Cook 25 minutes or so. Allow to cool in tin and slice.

It makes around 15 lovely chewy biscuits.