In a saucepan over medium heat, combine 2 cups milk, 2 cups sugar, beaten eggs, nutmeg & salt. Bring to a simmer, stirring constantly. Cook for 5 minutes until mixture thickens slightly.
While custard is cooking, in a small bowl combine 2 envelopes of gelatin in ½ cup cold milk. Let sit for 5 minutes.
Remove custard from the heat and pour mixture over the gelatin. Whisk well to remove any lumps. Add vanilla. Let custard cool to room temperature, about 30 minutes.
For the crust, crush graham crackers into fine crumbs using a food processor. Add melted butter and 3 tbsp. sugar. Press into bottom of 9x13 pan, reserving ¼ cup for the top.
In a metal bowl whip heavy whipping cream until stiff peaks form. Gently fold whipped cream into cooled custard until well combined. Pour over crust and sprinkle with reserved graham cracker crumbs.
Chill for at least 2 hours in the refrigerator until set. Cut into bars & serve.