First, in the crockpot add in the evaporated milk, velveeta cheese, broccoli and the salt and pepper. You do not have to thaw the broccoli first.
Turn the crockpot on high and cook for 3 hours. Each hour come back and give the casserole a stir so the cheese on the outside doesn't burn.
In the last 30 minutes, mix together the crushed crackers with butter and bake in the at 350F. The crackers will take about 15 minutes and you'll need to stir them every 5 minutes until golden. To add, you can skip this step fi you'd like.
Now after the 3 hours is up, before serving spread the crackers across the top of the casserole or serve them across in the serving dishes.