Heat oven to 300°F (150°C). Spread almonds, cashews, pumpkin seeds, sunflower seeds, and sesame seeds on a dry baking sheet and toast for 8 minutes until the sesame seeds are pale gold. Set aside, keeping the nuts warm.

Line a large baking sheet with a silicone mat or greased parchment. In a heavy-bottomed saucepan over medium heat, stir sugar and water together until dissolved, about 2 minutes. Add honey, stop stirring, and cook, swirling occasionally, for 10 to 14 minutes until the caramel turns deep amber (340°F to 350°F / 170°C to 175°C).

Remove from heat and stir in butter, sea salt, and baking soda. The mixture will foam up. Stir for 15 seconds until butter melts and foam settles, then stir in vanilla extract.

Add the warm nut and seed mixture all at once and fold together with 6 to 8 turns until everything is coated.

Pour onto the prepared baking sheet and spread to roughly 1/4 inch (6mm) thick. Leave undisturbed for 20 to 25 minutes until fully set. Crack into pieces and arrange glossy-side up on a board to serve.