For blackberry sauce: 5 cups fresh blackberries, divided (you can also use frozen) 3/4 cup water, divided 1/3 cup sugar 1 Tablespoon lemon juice 2 teaspoons cornstarch 1/4 teaspoon ground cinnamon 1 Tablespoon unsalted butter
2 cups fresh blackberries, washed and rinsed 1 pint gf vanilla ice cream 1/4 cup toasted slivered almonds
For blackberry sauce: Using a blender or a food processor, blend 1 cup blackberries and 1/2 cup water until smooth. Strain through a sieve.
In a medium saucepan, combine strained juice with 1/4 cup water, sugar, lemon juice, cornstarch and cinnamon. Bring to a boil. Cook for 1 minute over medium heat. Remove from heat and whisk in butter until thoroughly melted and mixture has emulsified.
To assemble: Place a spoonful or two of fresh blackberries in the bottom of a dessert dish. Top with one or two scoops of ice cream and then pour two spoonfuls of the blackberry sauce over the ice cream. Top with more fresh blackberries and sprinkle with toasted almonds. Serve immediately.
The blackberry sauce can be made ahead and stored in the refrigerator for up to 1 week.