Heat oven to 400 F.
Mix all ingredients together.
Spoon onto sheet pan which is covered with greased parchment / baking paper.
Cover the mixture with a piece of parchment or waxed paper. Even out the mixture to about 1/8 inch. I find a straight edge, like a ruler, works well, though you can use a rolling pin or wine bottle too. The important thing is not to let it be too thin around the edges or that part will overcook before the center firms up. So after you spread it out, remove the paper and go around the edges with your finger and push the thin part inwards to even it up.
Bake until the centre is no longer soft, about 15-18 minutes. If it starts to get more than a little brown around the edges, remove from oven. Let cool completely – it will continue to crisp up.
Break into pieces.