Preheat oven to 300.

In large bowl using electric beater, beat butter sugar and salt until smooth and fluffy

Mix baking soda and vanilla, then add to butter mixture.

Add the flour 1 cup at a time mixing well.

Gently stir in Rice Krispies.

Lightly butter baking sheets, Spoon 2tbsp size mounds of dough on cookie sheet about 3 inches apart.

Bake 15 minutes, then remove the pans from oven and gently flatten cookies with spatula.

Rotate pans from back to front and top to bottom, continue backing until cookies are golden brown on bottom and lightly cracked on top, about 25 minutes

Let cool slightly and transfer to racks to cool completely.