This was originally going to be a cookies and cream cheesecake, but I was making it for a Chocothon and I wanted it to be more chocolatey than that, so I went for a milk chocolate cheesecake batter; hence, Cookies and Milk. I have not yet achieved a cookie that stays crunchy in the cheesecake itself, but neither have I heard any complaints.
1 1/4 cup flour
1/3 cup cocoa powder (not alkalized)
scant 1/4 tsp. baking soda
1/2 cup (1 stick) salted butter, softened
1 egg
1/2 cup sugar
1 Tbsp. vanilla extract
5 Tbsp. butter, melted (for crust)
8 oz. milk chocolate, coarsely chopped
1/2 cup heavy cream
1 1/2 lbs. cream cheese, softened
1 cup sugar
3 eggs
8 oz. sour cream
1 Tbsp. vanilla extract
For the cookies, preheat oven to 325°F. You should really try to use air-cushioned cookie sheets for this recipe, as you want to be able to bake the cookies to a thorough crunchiness without burning them.
Sift together the flour, cocoa, and baking soda. In a separate bowl, cream the butter and sugar until fluffy, beat in the egg, and beat in the vanilla. Stir in the flour mixture until uniform. The dough will be very sticky. Scrape the dough onto a piece of plastic wrap or waxed paper, shape into a log aboue 1 1/2 inch in diameter, wrap up well, and freeze until firm, about 1/2 hour. Cut 1/8 inch slices, arrange on ungreased air-cushioned cookie sheets, and bake about 25 minutes, until quite firm to the touch. Cool completely. (The cookies can be made ahead and stored in an airtight container for several days.)
You now want to process the cookies into about 1 1/2 cups crumbs and 2 cups of chunks. You can break some up and crush the rest by hand, if you like, but I find it easiest to grind them all up in the food processor (which I normally don't use for making crumbs, since it makes such unevenly sized pieces) and then straining the resulting mixture through a punched-metal colander.
Preheat oven to 375°F. Prepare a 9x3 inch springform pan by wrapping the bottom in aluminum foil and then attaching the side. Set aside about 1/4 cup of crumbs and reserve to finish the cheesecake. Put the remaining 1 1/4 cup of crumbs in a medium bowl, pour the melted butter over it, and stir with a fork until thoroughly moistened. Pour the crumb mixture into the prepared springform pan and press it evenly over the bottom. Bake at 375° for about 10 minutes, until firm. Remove from the oven and cool completely, then lightly butter the sides of the pan. Wrap the outside of the pan in two layers of heavy-duty aluminum foil. (The cheesecake will be baked in a water bath, so the foil wrapping is necessary to prevent water from leaking in and making the crust soggy.) Reduce the oven temperature to 325°F, and refrigerate the crust until the batter is ready.
Place the chopped milk chocolate in a small bowl, bring the heavy cream to a boil in a small saucepan, and pour over the chocolate. Give it about 30 seconds to melt, then whisk until smooth. Cool until tepid.
In a large bowl, cream the cream cheese with the sugar. Beat in the eggs, one at a time, scraping down the sides after each addition. Beat in the sour cream and vanilla extract, then the milk chocolate ganache. Scrape the sides again thoroughly and beat until uniform, then fold in the cookie chunks. Scrape the batter into the prepared springform pan, then place it in a large roasting pan or jelly roll pan. Add enough very hot water to the outer pan to come at least half an inch up the sides of the springform pan, then bake at 325°F for about one hour. The center will seem quite jiggly but no longer liquid when it's done. Turn off the heat, prop the oven door just slightly open, and leave the cheesecake in the oven to slow-cool for another hour. Remove it from the oven and the water bath and cool completely on a wire rack, then refrigerate for at least 4 hours and preferably overnight.
To serve, run a thin-bladed knife around the edge of the cheesecake and remove the side of the springform pan. Supporting the cheesecake with one hand, press the reserved crumbs onto the sides with the other hand to make a nice-looking side. Cover the top of the cheesecake with plastic wrap, invert onto a cookie sheet, remove the bottom of the springform pan, and peel off the foil. Re-invert the cheesecake onto a serving platter, remove the plastic wrap, and sprinkle any remaining cookie crumbs on top in a decorative pattern.