Brew your coffee. Make 1 cup of strong coffee using your preferred method (drip, French press, or espresso diluted with hot water). Stronger coffee stands up better to the toffee and milk.
Warm the milk. In a small saucepan or microwave, heat the milk until hot but not boiling.
If you have a frother, froth it for extra creaminess.
Flavor the milk. Stir in the toffee sauce (or caramel + a drop of butter extract), the nut extract, and a pinch of sea salt. Taste and adjust sweetness with brown sugar or maple syrup if needed.
Combine with coffee. Pour the flavored milk into your hot coffee and stir well. If you prefer a layered look, pour the milk slowly over the coffee.
Finish and garnish. Top with whipped cream if you like, then sprinkle with crushed toffee or chopped toasted nuts for a little crunch.
For an iced version: Chill the coffee, then build it over ice.
Use cold milk and the same flavorings. Stir well and finish with whipped cream or a drizzle of sauce.