Preheat oven to 350°F (180°C), or 325°F (170°C) for convection ovens.
Wrap the outside of a 9-inch springform pan with 3-4 layers of aluminum foil, covering bottom and sides but not inside.
Crush Oreo cookies into fine crumbs using a food processor or freezer bag and rolling pin.
Mix crushed cookies with melted butter and press evenly onto bottom of the prepared pan, creating a slight lip.
Bake crust for 8 minutes in preheated oven, then remove and keep oven on.
Dissolve instant coffee powder in Kahlua in a small bowl.
Beat cream cheese and sugar in a large bowl until smooth, scraping sides regularly.
Beat in sour cream until smooth.
On low speed, beat Kahlua and coffee mixture into cream cheese mixture; add extra Kahlua if desired.
Whisk eggs and yolks together, then add to cream cheese mixture in 2-3 batches, mixing gently without overbeating.
Place springform pan in large roasting pan; pour cheesecake batter into pan and smooth top.
Pour hot water into roasting pan to a depth of 1/2 to 1 inch around springform pan.
Bake cheesecake for 50-60 minutes or until center wobbles like pudding when gently shaken.
Cool cheesecake in water bath until water reaches room temperature, then remove springform pan and cool on wire rack until pan is no longer warm.
Cover top and chill cheesecake in refrigerator for at least 6 hours or overnight.
Chop chocolate finely and place in heatproof bowl.
Heat cream and Kahlua together until almost boiling; pour over chocolate and let sit 3 minutes.
Whisk ganache until smooth, microwaving briefly if needed to remove lumps.
Unclamp chilled cheesecake from pan and remove foil.
Pour ganache over cheesecake top, smoothing evenly; allow drips if desired.
Return cheesecake to fridge until ready to serve.
Slice with a thin, sharp knife, wiping blade clean between slices for neat portions.