Grease a 9" tart shell and preheat oven to 350F.
Place walnuts, sugar and melted butter in a food processor and pulse until all the ingredients have combined.
Scoop walnut mixture in the tart shell and use your fingers or the back of a spoon to evenly spread the paste into the shell.
Prick the shell with a fork.
Bake for 12-15 minutes until the shell is golden. If the shell puffed, use the back of a spoon to press it back as soon as you take it out of the oven. Let cool
Place chopped chocolate and butter in a large bowl.
Pour heavy cream in a saucepan and place over the stove medium heat. Once you notice some bubbles at the edges of the pan, remove from stove and pour cream over chocolate.
Wait a few minutes before mixing to allow the hot cream to melt the chocolate and butter.
Use a rubber spatula or a hand whisker to mix the filling until smooth.
Pour chocolate filling into the walnut shell and spread it evenly.
Allow to cool and firm for about 30 minutes.
When ready to serve, sprinkle some melted chocolate or top with fresh fruits.