crockpot Graham Cracker Cookies

2 c semi sweet chocolate chips
2 1 oz. squares unsweetened baking chocolate, shaved
4 c. crushed graham crackers, divided
2 cans ( 140z.)sweetened condensed milk
1C finely chopped walnuts
Place chocolate in slow cooker. Cover. Cook on high 1 hour, stirring every 15 minutes, or until chocolate is melted. Stir milk into melted chocolate. Add 3 C graham cracker crumbs, 1 c at a time, stirring after each addition. Stir in nuts. Stir in remaining graham cracker crumbs to reach consistence of cookie dough.
Drop by teaspoons on greased baking sheet. Bake at 325 degrees for 7-9 minutes, or until the tops of cookies begin to crack. Remove from oven. Cool 1-2 minutes before transferring to cooling racks. Keep remaining dough mixture warm by covering and turning the slow cooker to warm.