Line an 8-inch-square baking pan with parchment paper, letting the excess paper hang over the sides.

Seal the cookies in a ziplock bag and use a rolling pin to gently crush them into chunks.

In a medium saucepan over medium-high heat, bring 1 inch of water to a simmer.

Meanwhile, stir together chocolate chips and condensed milk in a heat-safe bowl that will fit snugly over the saucepan without touching the water.

Reduce heat to low and place the bowl over the saucepan. Stir the ingredients until smooth, about 6 minutes.

Fold 2 cups of the crushed cookies and ¼ cup of rainbow sprinkles into the chocolate mixture, then pour it into the pan.

Spread fudge evenly with a spatula.

Gently press the remaining cookies and some additional rainbow sprinkles into the fudge.

Refrigerate until firm, about 2-3 hours.

Use the parchment to lift the fudge out of the pan, and cut into 36 pieces.