(Prep the base)Place the cookies or graham crackers in a bag and crush finely with a rolling pin. In a microwave-safe cup, cover and heat the butter at 600 W for 30–40 seconds until melted.
In a bowl, mix the crushed cookies with the melted butter. Pour into the cake pan and press firmly into an even layer to make the crust (use a small jar to press around the circle).
Make the filling In a bowl, beat cream cheese and sugar until smooth.
In a small bowl,dissolve the gelatin in 2 tbsp. water, cover, and microwave at 600 W for 20 seconds to melt. In a small saucepan, combine milk and egg yolk and heat gently over low heat—do not let it boil. Stir in the melted gelatin, mix well, and remove from the heat.
Pour the saucepan mixture into the cream-cheese bowl and whisk well. Add heavy cream and lemon juice; mix until evenly combined.
(Set) Pour into the cake pan over the cookie crust, cover, and chill 3–4 hours until set. Slice and serve.