1cupfresh raspberriesplus additional berries for garnish
To make pasta dough
Combine all pasta ingredients in a stand mixer and mix with the flat beater until ingredients are mostly together, about 30 seconds to 1 minute.
Switch to the dough hook and beat on speed 2 for 2-3 minutes. If dough is crumbly, add water 1 tbsp at a time until it comes together.
Remove dough and hand knead for 2 minutes. Cover with plastic wrap and let rest for 30 minutes to an hour.
To make filling
Meanwhile, in a double boiler, melt together white chocolate and 1/4 cup cream. Set aside 1/3 cup of the mixture to use for a sauce later.
Whisk together mascarpone, vanilla, and 1 tbsp cream just until combined and soft. Fold in white chocolate mixture a little at a time until fully incorporated. Do not overmix.
To assemble ravioli
Divide pasta dough into 4 pieces. Roll each piece out into thin, oblong shape. Feed through pasta roller on widest setting. Fold in thirds or quarters and roll through again until it's smooth and has no holes. Then run pasta sheet through on setting 2 twice, then setting 3 twice. You can go up to 4 if you'd like.
If using a mold, flour ravioli maker before laying pasta sheet on top. Lightly flour top of pasta and press plastic mold into top to create indentations.
Fill each indentation with about a tsp of chocolate mascarpone filling. Top with second sheet of pasta dough, pressing lightly into each indentation while placing on top to avoid trapping air bubbles. Lightly flour, and roll the top with a rolling pin until you can see the perforations. Flip over, remove ravioli from mold, and separate pieces.
Repeat until filling is used up, piecing together pasta scraps when necessary. Roll any extra dough out to setting 4 or 5 and cut into fettuccini for use in another dish.
Use ravioli immediately, or refrigerate or freeze for later.
To make raspberry sauce
Melt butter in a small saucepan. Add sugar and raspberries and cook over medium heat, stirring frequently, until sugar is dissolved and raspberries have broken down. Sauce will be tart - add more sugar if you prefer it sweeter.
Mix cornstarch and water until smooth, and pour mixture into saucepan, stirring constantly. Sauce should thicken quickly.
Strain sauce through a fine mesh sieve and discard seeds.
To assemble dish
Bring a pot of water to a rolling boil. Cook ravioli for about 9 minutes. All pieces should be floating. Drain and serve about 5 to a person.
Heat reserved white chocolate sauce in the microwave for 30 seconds and stir. Heat for another 15 seconds, stir, and drizzle on top of ravioli.
Drizzle raspberry sauce over ravioli and top with fresh raspberries. Serve immediately.