• Combine the skim milk, 1 tablespoon of gelatin, and ¼ cup of sugar in a saucepan; whisk together over medium heat until gelatin and sugar have completely dissolved.
• Don't allow the milk to fully boil; remove it from the heat just before it starts to bubble and boil.
• Stir in the vanilla extract and optional food coloring after removing from heat.
• Allow the saucepan full of hot milk to cool a bit before trying to pour it into the dessert cups (boiling liquid will melt these cheapie dollar-store plastic cups!)

Make the berry topping

• Pour ¼ cup cold water into a small bowl and sprinkle with 1 teaspoon of gelatin; set aside while you prepare the other ingredients.
• Combine the frozen raspberries, frozen strawberries, 2 tablespoons and 2 teaspoons of water in a small saucepan. Put the lid on, and crank the heat up to medium-high until the fruit is thawed and the mixture has begun to boil.
• Turn the heat down to low and allow the mixture to simmer for about 20 to 30 minutes, stirring occasionally to mash the fruit up.
• If the mixture begins to boil over, you may want to remove the lid, but you'll want the fruit to be liquid-y in the end -- so you may need to add some extra water to compensate for evaporation. You'll want to end up with about 1 cup of fruit when you're done.
• Stir the water/gelatin mixture into the simmering berry sauce and remove from heat.

Assembling the panna cotta cups

• After letting the panna cotta milk mixture cool for 30 minutes, it's probably cool enough to pour into the dessert cups. I like to use a big measuring cup with a spout for this; less chance of spilling it everywhere.
• Immediately put the little cups in the fridge and let them sit and firm up for about 45 minutes while the berry mixture cools on the counter.
• Pour the berry mixture on top of the slighty-firm panna cotta. Again, I like to use a measuring cup with a spout for this because I'm really bad at pouring.
• Put the little cups back in the fridge for about 4 hours.