Spread the pecans evenly on a baking sheet and toast in the oven for 8 to 10 minutes. Remove and let cool before coarsely chopping.
Place a scoop of ice cream in a parfait glass and top with caramel sauce, crushed blackberries, and pecans. Repeat 2 more times and then top with a large dollop of whipped cream.
Place the heavy cream and vanilla bean and seeds in a small saucepan and bring to a simmer over medium heat. Remove the cream from the heat and let sit while making the caramel.
Whisk together the sugar and water in a medium non-reactive saucepan over high heat. Cook until dark golden brown, about 10 to 12 minutes. Remove the caramel from the heat and immediately add the cream slowly, stirring constantly with a wooden spoon. Return to the heat and cook until the mixture becomes smooth. Remove from the heat and stir in the butter and salt. Transfer to a bowl and serve immediately.
Combine the blackberries, sugar, and cassis in a medium bowl and stir well. Let sit at room temperature for 30 minutes. After 30 minutes, use a fork to crush the blackberries.