To make the Bundts (have all ingredients at room temperature):
Preheat the over to 350F.
Prepare the bundtlette pan and place on a baking sheet (see tips above).
Sift the flour into a medium bowl and whisk in the baking soda and salt. Set aside.
Cream together the sugar, butter and about ¾ of the vanilla beans, using the paddle attachment of your stand mixer on medium-high speed.
Lower the speed and add the eggs one at a time. Turn the mixer to beat well and fully incorporate after each addition.
Add the juice and zest and beat to incorporate.
Turn the mixer down to low (stir setting) and add the flour in three additions, alternating with the sour cream and starting and ending with the flour.
Turn up up the mixer to medium (about 4) and beat well to fully incorporate.
Fill the bundtlette molds and bake on the middle rack for 30-35 minutes.
Test for readiness, remove from the oven and allow to cool on a rack before turning them out.
To make the glaze:
In a heatproof bowl, gently melt the chocolate.
Stir in the champagne, juice, vanilla bean and zest until well combined.
You may add more or less juice/champagne to suit your desired consistency.