Preheat the oven to 375 degrees F.
Tip the almonds, sunflower seeds and pumpkin seeds onto a baking sheet. Toast until they begin to color, 10 to 12 minutes. Allow to cool.
Melt the chocolate in a glass bowl over a pan of simmering water (or in the microwave for 1 to 2 minutes) and stir until smooth and glossy. Set aside.
Spray a 9-by-12-inch baking sheet with nonstick cooking spray.
Add the granulated sugar, butter, brown sugar, kosher salt and 2 tablespoons of water to a heavy-bottomed saucepan fitted with a candy thermometer. Cook over medium-high heat, swirling the pan occasionally, until the thermometer registers 300 degrees F, 5 to 8 minutes. Remove from the heat and stir in the vanilla. Sprinkle in the baking soda and mix. Pour onto the prepared baking sheet and tip the baking sheet to spread the toffee evenly. Let it cool and set, about 6 minutes.
Drizzle the melted chocolate over the toffee. Scatter the toasted nuts and seeds, raisins and mini chocolate candy over the melted chocolate and sprinkle with the sea salt. Let set for 2 hours, then break the toffee into shards.