For those interested, here's the recipe I used.
BEST HOMEMADE PLAYING DOUGH
Amount Measure Ingredient -- Preparation Method
1 cup all-purpose flour
1/2 cup salt
1 cup water
1 tsp cream of tartar
1 Tbl vegetable oil
1 drop food coloring
Mix all ingredients in a pan. Heat over medium to low heat for 3-5 minutes. Store in an airtight container or in locking plastic bags.
I use a whisk to get out the lumps, then use a rubber spatula to stir while cooking, although not sure if this is necessary. It comes together pretty quick, but I have a gas range so not sure if this makes a difference. Seem to recall that when I used the electric it took a little longer. Stir constantly. While cooking you will notice that it will start to get lumpy, sort of like scrambled eggs. Just keep stirring. It's done when it forms a ball and no longer looks wet.