How can I stuff MnMs inside a chocolate truffle cake?

This recipe for M&M cookie dough truffles are as follows:

The ingredients include: 2 1/2 cups all-purpose flour, 1 teaspoon salt, 1 cup (2 sticks) butter or margarine, room temperature, 3/4 cup granulated sugar, 3/4 cup packed brown sugar, 1 teaspoon vanilla, 1/3 cup skim milk, 1 tube of mini M&M’s (or two tubes if you like more M&M’s), 2 cups of Hershey's milk chocolate chips.