Prepare the Ramekins:

1. Preheat oven: Heat oven to 425°F (220°C).
2. Butter ramekins: Generously butter the inside of ramekins, making sure to coat all surfaces.
3. Dust with cocoa: Add cocoa powder to one ramekin, tilt and tap to coat all surfaces, then pour excess into next ramekin. Repeat until all are coated.
4. Place on baking sheet: Set prepared ramekins on a baking sheet for easy handling.

Make the Chocolate Base:

1. Melt chocolate and butter: In double boiler or microwave, melt chocolate and butter together, stirring until smooth. If using microwave, heat in 30-second intervals, stirring between each.
2. Add coffee: If using instant coffee, dissolve in 1 tbsp hot water and stir into chocolate mixture.
3. Cool slightly: Let mixture cool for 2-3 minutes.

Prepare the Batter:

1. Beat eggs: In medium bowl, whisk together whole eggs, egg yolks, and sugar until thick and pale (about 2-3 minutes by hand, 1 minute with electric mixer).
2. Add vanilla: Beat in vanilla extract.
3. Combine chocolate: Gradually whisk the warm chocolate mixture into the egg mixture until smooth.
4. Add flour: Sift flour and salt over mixture and gently fold in until just combined. Don’t overmix.

Fill and Bake:

1. Divide batter: Spoon batter evenly among prepared ramekins, filling each about ¾ full.
2. Bake immediately: Bake 12-14 minutes for 6-oz ramekins (10-12 minutes for 4-oz) until edges are set and centers still jiggle slightly when shaken.
3. Rest briefly: Let rest 1 minute in ramekins.

Serve:

1. Run knife around edges: Gently loosen cakes from ramekins with thin knife.
2. Invert: Working quickly, invert each ramekin onto serving plate and let sit 10 seconds before lifting off ramekin.
3. Dust and garnish: Dust with powdered sugar and add desired garnishes.
4. Serve immediately: Serve right away while centers are still molten.