Line a large baking sheet with parchment paper and place it close to the stove. Have a tablespoon or small cookie scoop ready because the praline mixture will begin setting quickly once it thickens.

If the pecans are not already toasted, spread them on a baking sheet and toast at 350°F (175°C) for 6 to 8 minutes, until fragrant. Let them cool before using.

Add the granulated sugar, brown sugar, evaporated milk, butter, and salt to a heavy-bottomed 3- to 4-quart saucepan.

Set the saucepan over medium heat: Stir gently until the butter melts and the sugars dissolve into a smooth mixture, about 3 to 4 minutes.

Increase the heat to medium-high and bring the mixture to a steady boil. Attach a candy thermometer so the tip is submerged in the syrup but does not touch the bottom of the pan.

Cook, stirring only occasionally and carefully, until the mixture reaches 238°F to 240°F (114°C to 116°C). This usually takes about 8 to 12 minutes after the mixture reaches a full boil.

As soon as the syrup reaches the target temperature, remove the saucepan from the heat. Hot sugar can cause severe burns, so keep hands and utensils clear of splashes.

Stir in the vanilla extract and toasted pecans until evenly distributed.

Let the mixture stand undisturbed for about 3 to 5 minutes. It should remain fluid but begin to thicken slightly around the edges.

Stir vigorously with a wooden spoon for 1 to 3 minutes. The mixture should gradually thicken, become slightly lighter, and lose some of its glossy sheen.

Stop stirring when a spoonful dropped back into the pan briefly holds its shape instead of immediately melting into the mixture. Do not wait until it becomes stiff or dry.

Working quickly, drop heaping tablespoons of the mixture onto the prepared parchment, leaving about 1 inch (2.5 cm) between pralines.

If a praline spreads unevenly, gently nudge the edges into a round shape with the back of the spoon while it is still soft.

Leave the pralines undisturbed at room temperature for about 30 minutes, or until fully set and firm enough to lift cleanly from the parchment.

Once completely cool and set, serve immediately or transfer to an airtight container.