Make the crust first by mixing crushed graham crackers with melted butter until it looks like wet sand. Press about a tablespoon of this mixture into the bottom of each of 6 small cups or jars. Refrigerate while you work on the mousse.
Blend 2 cups fresh strawberries with 1/4 cup granulated sugar and 1/2 tsp lemon juice in a food processor until completely smooth. Pour the puree through a fine mesh strainer to remove the seeds (you'll get a silky texture this way). This step takes just two minutes but makes a huge difference.
In a small bowl, sprinkle gelatin over 1/4 cup cold water and let it sit for two minutes to bloom. Then microwave it for 15 seconds until completely dissolved and clear. Don't overheat it or the gelatin loses its thickening power.
Whip 1 cup heavy cream with 2 tbsp powdered sugar and 1 tsp vanilla bean paste until you get soft peaks. The cream should look fluffy but still drip a little from your whisk — don't take it to stiff peaks or the final mousse gets grainy.
Fold the dissolved gelatin into the strawberry puree, stirring really gently for about one minute so it combines evenly. Next, fold in the whipped cream in two batches, being super careful not to deflate all those beautiful air bubbles. I always use a rubber spatula and turn the bowl as I fold rather than overmixing.
Stir 1/4 cup condensed milk into the mousse mixture until you don't see any white streaks. This adds richness that makes the strawberry mousse cups cozy taste almost luxurious.
Divide the mousse between your prepared cups, filling them about three-quarters full. Refrigerate for at least 4 hours until the mousse sets completely (overnight is even better). Top with fresh mint leaves just before serving.