Line a 1lb loaf pan with parchment paper, ensuring it fits snugly against the sides.
In a medium saucepan over medium-high heat, melt the butter and condensed milk together. Stir occasionally and cook for about 5 minutes until smooth and slightly thickened.
2 tablespoons salted butter, 14 ounces sweetened condensed milk
Stir in the vanilla bean paste and sea salt.
1 teaspoon vanilla extract or paste, ½ teaspoon sea salt
Add both semi-sweet and milk chocolate chips, stirring continuously until fully melted and smooth.
Quickly fold in the toasted almonds and mini marshmallows, stirring just enough to evenly distribute. Be careful not to overmix, as the marshmallows may melt. Set aside a few almonds and marshmallows to sprinkle on top for a decorative finish.
1 cup mini marshmallows, ½ cup almonds, Pour the mixture into the prepared loaf pan and spread evenly. Sprinkle the reserved marshmallows and almonds on top, pressing them in gently.
Refrigerate for at least 2 hours until fully set. Once firm, cut into squares and enjoy.